
Terms andPhrases 



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LIBRARY OF CONGRESS. 



D STATES OF OIVKU \. 



DICTIONARY 



ELECTRICAL WORDS, TERMS 
AND PHRASES. 



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EDWIN J. HOUSTON, A. M. 



Professor of Natural Philosophy and Physical Geography in the Central High 

School of Philadelphia ; Professor of Physics in the Franklin Institute 

of Pennsylvania ; Electrician of the International 

Electrical Exhibition, etc. 



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THE W. J. JOHNSTON CO., Ld., 

Times Building , 

NEW YORK. 



CopruiGHT, 1889, 

BY 

The W. J. Johnston Co., Ld. 



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PREFACE. 



The rapid growth of electrical science, and the almost 
daily addition to it of new words, terms and phrases, 
coined, as they too frequently are, in ignorance of those 
already existing, have led to the production of an 
electrical vocabulary that is already bewildering in its 
extent. This multiplicity of words is extremely dis- 
couraging to the student, and acts as a serious obstacle 
to a general dissemination of electrical knowledge, for 
the following reasons : 

1. Because, in general, these new terms are not to be 
found even in the unabridged editions of dictionaries. 

2. The books or magazines, in which they were first 
proposed, are either inaccessible to the ordinary reader, 
or, if accessible, are often written in phraseology unin- 
telligible except to the expert. 

3. The same terms are used by different writers in 
conflicting senses. 

4. The same terms are used with entirely different 
meanings. 

5. Nearly all the explanations in the technical dic- 
tionaries are extremely brief as regards the words, terms 
and phrases of the rapidly growing and comparatively 
new science of electricity. 

In this era of extended newspaper and periodical pub- 
lication, new words are often coined, although others, 



II PREFACE. 

already in existence, are far better suited to express the 
same ideas. The new terms are used for a while and 
then abandoned; or, if retained, having been imperfectly- 
defined, their exact meaning is capable of no little 
ambiguity ; and, subsequently, they are often unfortun- 
ately adopted by different writers with such varying 
shades of meaning, that it is difficult to understand 
their true and exact significance. 

Then again, old terms buried away many decades ago< 
and long since forgotten, are dug up and presented in 
such new garb that their creators would most certainly 
fail to recognize them. 

It has been with a hope of removing these difficulties 
to some extent that the author has ventured to present 
this Dictionary of Electrical Words, Terms and Phrases 
to his brother electricians and the public generally. 

He trusts that this dictionary will be of use to 
electricians, not only by showing the wonderful extent. 
and richness of the vocabulary of the science, but also 
by giving the general consensus of opinion as to the sig- 
nificance of its different words, terms or phrases. It is, 
however, to the general public, to whom it is not only 
a matter of interest but also one of necessity to fully 
understand the exact meaning of electrical literature, 
that the author believes the book will be of greatest 
value. 

In order to leave no doubt concerning the precise 
meaning of the words, terms and phrases thus defined^ 
the following plan has been adopted of giving, 

(1) A concise definition of the word, term or phrase* 



PREFACE. Ill 

(2) A brief statement of the principles of the science 
involved in the definition. 

(3) Where possible and advisable, a cut of the appar- 
atus described or employed in connection with the 
word, term or phrase defined. 

It will be noticed that the second item of the plan 
makes the Dictionary approach to some extent the 
nature of an Encyclopedia. It differs, however, from 
an encyclopedia in its scope, as well as in the fact that 
its definitions in all cases are concise. 

Considerable labor has been expended in the collection 
of the vocabulary, for which purpose electrical literature 
generally has been explored. In the alphabetical ar- 
rangement of the terms and phrases defined, much per- 
plexity has arisen as to the proper catch-word under 
which to place them. It is believed that part of the 
difficulty in this respect has been avoided by the free 
use of cross-references. 

In elucidating the exact meaning of terms by a brief 
statement of the principles of the science involved there- 
in, the author has freely referred to standard text books 
on electricity, and to periodical literature generally. He 
is especially indebted to works or treatises by the fol- 
lowing authors, viz.: S. P. Thompson, Larden, Cum- 
ming, Hering, Prescott, Ayrton, Ayrton and Perry, Pope, 
Lockwood, Sir Wm. Thomson, Fleming, Martin and 
Wetzler, Preece, Preece and Sivewright, Forbes, Max- 
well, De Watteville, J. T. Sprague, Oulley, Mascart and 
Joubert, Schwendler, Fontaine, Noad, Smee, Depretz, 
De la Rive, Harris, Franklin, Cavallo, Grove, Hare, 
Daniell, Faraday and very many others. 



IV PREFACE. 

The author offers his Dictionary to his fellow elec- 
tricians as a starting point only. He does not doubt 
that his book will be found to contain many inaccuracies, 
ambiguous statements, and possibly doubtful definitions. 
Pioneer work of this character must, almost of neces- 
sity, be marked by incompleteness. He, therefore, in- 
vites the friendly criticisms of electricians generally, 
as to errors of omission and commission, hoping in 
this way to be able finally to crystallize a complete 
vocabulary of electrical words, terms and phrases. 

The author desires in conclusion to acknowledge his 
indebtedness to his friends, Mr. Carl Hering, Mr. 
Joseph Wetzler and Mr. T. C. Martin for critical ex- 
amination of his proof sheets ; to Dr. GL Gr. Faught for 
examination of the proofs of the parts relating to the 
medical applications of electricity, and to Mr. C. E. 
Stump for valuable aid in the illustration of the book ; 
also to Mr. Geo. D. Fowle, Engineer of Signals of the 
Pennsylvania Railroad Company, for information con- 
cerning their System of Block Signaling, and to many 
others. 

Central High School, Edwin J. Houston. 

Philadelphia, Pa. 

September, 1889. 



A DICTIONARY 



OF 



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Abscissas, Axis of- 



— Ouc of the axes of co-ordi- 
nates used for determining the position of points in a curved 
line. 

Thus the position of the point D, Fig. B 
1, in the curved line O D R, is deter- 
mined by the vertical distances D 1, and 
D 2, of such point from two straight 
lines AB, and AC, called the axes of co- 
ordinates. AC, is called the axis of ab- 
scissas, and AB, the axis of ordinates. 
A, the point where the lines may be 
considered as starting or originating, is 
called thepoint of origin. (See Co-ordinates, Axes of.) 

Absolute.— Complete in itself. 

The terms absolute and relative are used in electricity in 
the same sense as ordinarily. 

Thus, a galvanometer is said to be calibrated absolutely 
when the exact current strengths required to produce given 
deflections are known ; or, in other words, when the absolute 
current, strengths are known ; it is said to be calibrated rela- 
tively when only the relative current strengths required to 
produce given deflections are known. 




2 A DICTIONARY OF ELECTRICAL 

The word absolute, as applied to the units employed in elec- 
trical measurements, was introduced by Gauss to indicate 
the fact that the values of such units are independent both 
of the size of the instrument employed and of the value of 
gravity at the particular place whore the instrument is used. 

The absolute units of length, mass, and time are more prop- 
erly called the C. G. S. units, or the eenti metre-gramme- 
second units. 

An absolute system of units based on the milligramme, 
millimetre, and second, was proposed by Weber, and was 
called the millimetre-milligramme-second units. It has been 
replaced by the C. G. S. units. 

Absolute Calibration. — (See Calibration, Absolute., 

Absolute Galvanometer. — (See Galvanometer, Abso- 
lute.) 

Absolute Units. — A term sometimes used to indicate the 
C. G. S. units, but now generally replaced by the term centi- 
met re-gramme-second units, or, more briefly, the C. G. S. 
units. 

Absolute Unit of Current. — A current of ten amperes. 
(See Ampere. Units, Practical.) 

Absolute Unit of Electromotive Force.— The one 
hundred millionth of a volt. (See Volt. Units, Practical.) 

Absolute Unit of Resistance.— The one thousand 
millionth of an ohm. (See Ohm. Units, Practical.) 

Absolute Vacuum. — (See Vacuum, Absolute). 

Absorption, Electric The apparent soaking of 

an electric charge into the glass or other solid dielectric of a 
Leyden Jar or Condenser. (See Charge. Condenser.) 

The capacity of a condenser, or its ability to hold an elec- 
tric charge, varies with the time the condenser remains 
charged. Some of the charge acts as if it soaked into the 
solid dielectric, and this is the cause of the residual charge. 
(See Charge, Residual.) Therefore, when the condenser is 



WORDS, TERMS AND PHRASES. 3 

discharged, loss electricity appears than was passed in; hence 
the term electric absorption. 

Absorptive Power. — The property possessed by many 
solid bodies of taking in and condensing gases within their 
pores. 

Carbon possesses marked absorptive powers. The absorp- 
tion of gases in this manner by solid bodies is known techni- 
cally as the occlusion of gases. (See Occlusion of Gases.) 

One volume of charcoal, at ordinary temperatures and pres- 
sures, absorbs of 

Ammonia 90 volumes 

Hydrochloric Acid .85 

Sulphur Dioxide .65 " 

Hydrogen Sulphide 55 " 

Nitrogen Monoxide 40 " 

Carbonic Acid Cas 35 " 

Ethylene 35 

Carbon Monoxide 9.42 " 

Oxygen 9.25 " 

Nitrogen 6.50 " 

Hydrogen 1.25 " 

(Saussure.) 

Acceleration. — The rate of change of velocity. 

Acceleration is thus distinguished from velocity : velocity 
expresses in tune the rate-of-change of position, as a velocity 
of three metres per second ; acceleration expresses in time 
the rate-of-change of velocity, as an acceleration of one centi- 
metre per second. 

Since all matter is inert, and cannot change its condition 
of rest or motion without the application of some force, ac- 
celeration is necessarily due to some force outside of matter 
itself. A force may therefore be measured by the accelera- 
tion it causes in a given mass of matter. 

Acceleration is termed positive when the velocity is in- 
creasing, and negative when it is decreasing. 

Acceleration, Unit of That acceleration which 



4 A DICTIONARY OF ELECTRICAL 

will give to a body unit -velocity in unit-time ; as, for ex- 
ample, one centimetre per second. 

Bodies falling' freely in a vacuum, and approximately so in 
air, acquire an acceleration which in Paris or London, at the 
end of a second, amounts to about 9S1 centimetres per second, 
or nearly 32.2 ft. per second, 
v 

a — — , or in other words, the acceleration equals the ve- 

T 

locity divided by the time. 
But, since the velocity equals the Distance, or the Length 

L 
traversed in a unit of time, v = — . 

T 
L 

V T L 

Therefore, a = — = = — , or, the acceleration equals the 

T T T~ 

1 

length, or the distance passed through, divided by the square 
of the time in seconds. 

These formulae represent the Dimensions of Acceleration. 

Accumulator, or Condenser.— A term often applied 
to an apparatus called a Leyden Jar or Condenser, which per- 
mits the collection from an electric source of a greater charge 
than it would otherwise be capable of giving. 

The ability of the source to give an increased charge is due 
to the increased capacity of a plate or other conductor when 
placed near another plate or conductor. (See Condenser. 
Jar, Leyden.) 

Accumulator, Storage or Secondary Cell. — 

Two inert plates dipping into a liquid incapable of acting 
chemicalty on either of them until after the passage of an 
electric current, when they become capable of furnishing an 
independent electric current. 



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WORDS. TERMS AND PHRASES. 5 

This use of the term accumulator is the one most commonly 
employed. (See Storage Cells or Accumulators.) 

Accumulator.— A term sometimes applied to Sir Win. 
Thomson's Electric Current Accumulator. 

The copper disc D, Fig-. 2, has 
freedom of rotation, on a horizon- 
tal axis at O, in a magnetic field, 
the lines of force of which, repre- 
sented by the dotted lines in the 
drawing, pass down perpendicu- 
larly into the plane of the paper. Fig. 2. 

If, now, a current from any source be passed in the direc- 
tion A, O, B, C, A, through the circuit A, O, B, C, A, which 
is provided with spring- contacts at O, and A, the disc will 
rotate in the direction of the curved arrow. This motion is 
due to the current acting on that part of the disc which lies 
between the two contacts — A and O. This apparatus is 
known as Barlow's Wheel. 

If, when no current is passing through the circuit, the disc 
be turned in the direction of the arrow, a current is set up in 
such a direction as would oppose the rotation of the disc. 
(See Lenzs Laic.) 

If, however, the disc be turned in the opposite direction to 
that of the arrow, induction currents will as before be pro- 
duced in the circuit. xVs this rotation of the disc tends to 
move the circuit O A, towards the parallel but oppositely 
directed circuit B 0, these two circuits, being parallel and 
in opposite directions tend to repel one another, and there will 
thus beset up induced currents that tend to oppose the motion 
of rotation, and the current of the circuit will therefore increase 
in strength. (Sec Electro-Dynamics). Should then a current be 
started in the circuit, and the original field be removed, the 
induction will be continued, and a current which, up to a cer- 
tain extent, increases or accumulates, is maintained in the 
circuit during rotation of the disc. (Larden.) 



6 A DICTIONARY OF ELECTRICAL 

Barlow's Wheel, when used in this manner, is known as 
Thomson's Electric Current Accumulator. 

Accumulator, Water-Dropping An appa- 
ratus devised by Sir W. Thomson lor increasing- the difference 
of potential of an electric charge. 

The tube X Y, Fig-. 3, connects with a 
reservoir of water which is maintained at 
the zero potential of the earth. The water 
b eseapes from the openings at G and D in 
small drops and falls on funnels provided, 
as shown, to receive the separate drops 




nd again discharge them. 



The vessels A, A', and B, B', which are 
electrically connected as shown, are main- 
tained at a certain small difference of potential, as indicated 
by the respective -f and — signs. 

Under these circumstances, therefore, C and D, will be 
charged inductively with charges opposite to those of A and 
B, or with — and -f electricities respectively. As the drops 
of water fall on the funnels, the charges which the funnels 
thus constantly receive, are given up to B' and A', before 
the water escapes. Since, therefore, B, B', and A, A', are 
receiving- constant charges, the difference of potential between 
them must continually increase. This apparatus operates 
on the same principle as the replenisher. The drops of water 
act as the carriers, and A, A', and B, B', as the hollow vessels. 
(See Replenisher.) 

Accumulators or Condensers ; L<aws of Accu- 
mulation of Electricity. — Sir W. Snow Harris, by the 
use of his Unit- Jar, and Electric Thermometer, deduced the 
following laws for the accumulation of electricity, which we 
quote f rora Noad's "Student's Text-Book of Electricity," re- 
vised by Preece : 

(1) "Equal quantities of electricity are given off at each 
revolution of the plate of an electrical machine to an un- 



WORDS, TERMS AND PHRASES. 7 

charged surface, or to a surface charged to any degree of 
saturation." 

(2) "A coated surface receives equal quantities of electricity 
in equal times ; and the number of revolutions of the plate is 
a fair measure of the relative quantities of electricity, all 
other things remaining the same." 

(3) "The free action of an electrical accumulation is esti- 
mated by the interval it can break through, and is directly 
proportional to the quantity of electricity." 

(4) "The free action is inversely proportional to the sur- 
face." 

(.")) " When the electricity and the surface are increased in 
the same ratio, the discharging interval remains the same; 
but if, as the electricity is increased, the surface is diminished, 
the discharging interval is directly as the square of the quan- 
tity of electricity." 

(G) "The resistance of air to discharge is as the square of 
the density directly." 

According to some later investigations, the quantity a 
plane surface can receive under a given density depends on 
the linear boundary of the surface as well as on the area of 
the surface. 

"The amount of electrical charge depends on surface and 
linear extension conjointly. There exists in every plane 
surface what may be termed an electrical boundary, having 
an important relation to the grouping or disposition of the 
electric particles in regard to each other and to surrounding 
matter. This boundary in circles or globes is represented by 
their circumferences. In plane rectangular surfaces, it is by 
their linear extension or perimeter. If this boundary be con- 
stant, their electrical charge varies with the square root of 
the surface. If the surface be constant the charge varies with 
the square root of the boundary. If the surface and boun- 
dary both vary, the charge varies with the square root of the 
surface midtijilied into the square root of the boundary.''' 



8 A DICTIONARY OF ELECTRICAL 

These laws apply especially to continuous surfaces taken as 
a whole, and not to surfaces divided into separate parts. 

By electrical charge Harris meant the quantity sustained 
on a given surface under a given electrometer indication ; by 
electrical intensity, he meant the indication of the electro- 
meter corresponding to a given quantity on a given surface. 
For further information see Condensers, Capacity of. 
A, C C — An abbreviation used in medical electricity for 
Anodic Closure Contraction, or the contraction observed on 
(losing the circuit when the anode is lying over the muscle. 

The term anode is sometimes, as above, used to indicate the 
positive terminal of an electric battery or source. (See Anode.) 
Achromatic. — Free from false coloration. 
Images formed by ordinary lenses do not possess the true 
colors of the object, unless the edges of the lenses are cut off 
by the use of a diaphragm; i. e., an opaque plate with a circu- 
lar central opening. The edges of the lenses disperse the light 
like an ordinary prism, and so produce rainbow-colored 
(prismatic) fringes in the image. The use of an achromatic 
lens is to obviate this false coloration. 

The ray of light entering the prism ABC, Fig. 4, 
sutlers dispersion (separation into prismatic colors). This 
dispersion in the same medium is proportional to the angle g, 
between the incident and emergent faces, called the refract- 
ing angle. 

If, now, another prism BCD, of 
the same material, whose refract- 
ing angle g', is equal to g, is com- 
bined with the first prism in the 
manner shown in Fig. 4, it will 
produce an equal but opposite dis- 
persion, so that the ray of light 
will emerge at E, free from rain- 
ed bow tints, but parallel to its origi- 
*%' k ' nal direction. 





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Glass / „ 




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WORDS, TERMS AND PHRASES. 



The variety of glass called crown glass produces only half 
as great dispersion of light as the variety called flint glass, 
under the same refracting angle g. If the prism A B C, 
of crown glass, Fig. 5, whose 
angle g, is twice as great as the 
refracting angle g', of the prism 
BCD, of flint glass, he con- 
nected with it in the manner 
shown, then the ray R, will he 
transmitted free from color, but 
will not emerge parallel to its 
original direction ; in other $% g , ,5. 

words, it suffers refraction or bending. (See Refraction.) 

The construction of achromatic lenses is based on this 
principle. 





Fig. G. 

The crown glass is generally made with two convex sur- 
faces ; the flint glass, with one concave and one plane sur- 
face, as shown in Fig. 6. 

Sometimes both surfaces of the flint glass are made curved, 
as in Fisr. 7. 




Fig. 7. 

Aclinic Line. — The magnetic equator, or a line on the 
earth's surface connecting places where the magnetic needle 
has no inclination or dip. 

The magnetic equator is not a circle, It cuts the geograph- 



10 A DICTIONARY OF ELECTRICAL 

ical equator at 2° E. long., and at 170° W. long. (See Inclina- 
tion Map or Chart.) 

Acoustic Engraving.— (See Engraving, Acoustic.) 

Acoustic Telegraph.— A non-recording system of tele- 
graphic communication, in which the dots and dashes of the 
Morse system, or the deflections of the needle in the needle 
system, are replaced hy sounds that follow one another at in- 
tervals that represent the dots and dashes, or the deflections 
of the needle, and thereby the letters of the alphabet. 

Steinheil and Blight each invented acoustic systems of teleg- 
raphy in which electro-magnetic bells are used. Morse in- 
vented a Sounder, for this purpose, which is used very 
generally. (See Sounder, Telegraphic.) 

For details of the apparatus and system see Telegraphy, 
American or Morse system of. 

Actinic Photometer.— (See Photometer, Actinic.) 

Actinic Kay*. — The rays of light, or other forms of radi- 
ant energy that possess the power of effecting chemical de- 
composition. (See Decomposition.) 

All rays of light, and even some of those invisible to the 
human e3'e, are actinic to some particular chemical substance 
or another. Whether the ether waves produce the effects of 
heat, light, or chemical decomposition depends on the nature 
of the material on which they fall, as ivell as on the character 
of the waves themselves. 

Actinism. — The chemical effects of light, as manifested in 
the decomposition of various substances. 

Under the influence of the sun's light, the carbonic acid ab- 
sorbed by the leaves of plants is decomposed in the living leaf 
into carbon, which is retained by the plant for the formation 
of its woody fibre or ligneous tissue, and oxygen, which is 
thrown off. 

The bleaching of curtains, carpets, and other fabrics ex- 
posed to sunlight is caused by the actinic power of the light. 
The photographic picture is impressed by the actinic power of 



WORDS, TERMS AND PHRASES. 11 

light on a plate covered with some sensitive metallic salt, 
generally silver. 

Action, Local An irregular dissolving or con- 
sumption of the zinc or positive element of a voltaic battery, 
by the fluid or electrolyte, when the circuit is open or broken, 
as well as when closed, or in regular action. 

Local action is due to impurities, such as carbon, iron, ar- 
senic, etc., in the positive plate. These impurities form with 
the positive element little voltaic couples, and thus direct the 
corrosive action of the liquid to portions of the plate near the 
impurities. Local action causes a waste of energy. It may 
be avoided by amalgamation of the zinc. (See Zinc, Amal- 
gamation of.) 

Action, Local A term proposed, but not gener- 
ally adopted, to indicate the wasteful currents in the pole 
pieces or cores of dynamo-electric machines. 

These cm-rents are now generally known as Eddy, Foacaidt, 
or Parasitical Currents. (See Car rents, Eddy, Foacaidt, 
Local, or Parasitical.) 

Action, Ulagnc-Crystallic (See Magne-Crystal- 

lie Action.) 

Action, Unit of A rate of working, which will 

perform one unit of work per second. 

In C. G. S. units, the activity of one erg per second. This 
unit is very small. One Watt, the practical unit of power, is 
equal to ten million ergs per second. (See Watt.) 

The unit of activity generally used for mechanical power is 
one horse-power, or 746 watts. (See Horse-power.) 

Activity. — The work done per second by any agent. 

Work-per-second, or, as generally termed in the United 
States, Power, or Rate of Doing Work. (See Power.) 

A. I>. C. — An abbreviation used in medical electricity for 
Anodic Duration Contraction. 

Adhesion. — The attraction that exists between unlike 
molecules. (See Attraction, Molecular.) 



12 A DICTIONARY OF ELECTRICAL 

Ad iat h erm an cy.— Opacity to heat. 

A substance is said to be diathermanous when it is trans- 
parent to heat. Clear, colorless crystals of rock salt are very 
transparent both to light and to heat. Rock salt, covered with 
a layer or deposit of lamp-black or soot, is quite transparent 
to heat. An adiathermanous body is one which is opaque 
to heat. 

Heat transparency varies not only with different sub- 
stances, but also with the nature of the source from which 
the heat is derived. Thus, a substance may be opaque to the 
heat from a non-luminous source, such as a vessel filled with 
boiling- water, while it is comparatively transparent to that 
from a luminous source, such as an incandescent solid, or the 
voltaic arc. 

A similar difference exists as regards transparency to 
light. A colorless glass will allow light of any color to pass 
through it. A blue glass will allow blue light to pass 
freely through it, but will completely prevent the passage 
of any red light ; and so with other colors. 

T]|»iiiu*' Condenser. — (See Condenser.) 

Affinity, < iieinieal Atomic attractions. 

The force that causes atoms to unite and form chemical 
molecules. 

Atomic, or chemical attraction generally results in a 
loss of the characteristic qualities, or properties, that dis- 
tinguish one kind of matter from another. In this respect 
it differs from adhesion, or the force which holds unlike 
molecules together. (See Adhesion.) If, for example, sulphur 
is mixed with lamp-black, no matter how intimate the mix- 
ture, the separate particles, Avhen examined by a glass, ex- 
hibit their peculiar color, lustre, etc. If, howerer, the sul- 
phur is chemically united with the carbon, a colorless, trans- 
parent, mobile liquid, called carbon bisulphide, results, that 
possesses a disagreeable, penetrating odor. 

Chemical affinity, or atomic combination, is influenced by 
a variety of causes, viz. ; 



WORDS, TERMS AND PHRASES. 13 

(1) Cohesion. Cohesion, by binding- the molecules more 
firmly tog-ether, opposes their mutual atomic attractions. 

A solid rod of iron will not readily burn in the flame of an 
ordinary lamp, but if the cohesion be overcome by reducing 
the iron rod to filings, it burns with brilliant scintillations 
when dropped into the same flame. 

(2) Solution. Solution, by imparting to the molecules 
greater freedom of motion, favors their chemical com- 
bination. 

(3) Heat. Heat favors atomic combination by decreasing 
the cohesion, and possibly, by altering the electrical rela- 
tions of the atoms. If too great, heat may produce decom- 
position. (See Dissociation.) 

(4) Light. Decomposition, or the lessening of chemical 
affinity through the agency of light, is called Actinism. Light 
also causes the direct combination of substances. A mix- 
ture of equal volumes of hydrogen and chlorine unites ex- 
plosively when exposed to the action of full sunlight. (See 
Actinism.) 

(5) Electricity. An electric spark will cause an explosive 
combination of a mixture of oxygen and hydrogen. Electric- 
ity also produces chemical decomposition. (See Electrolysis.) 

AgOlie. — A line connecting places on the earth's surface 
where the magnetic needle points to the true geographical 
north. 

The line of no declination or variat ion of a magnetic needle. 
(See Declination or Variation of Magnetic Needle.) 

As all the places on the earth where the magnetic needle 
points to the true north may be arranged on a few lines, it 
will be understood that the pointing of the magnetic needle 
to the true geographical north is the exception and not the 
rule. In many places, however, the deviation from the true 
geographical north is so small that thue direction of the needle 
may be regarded as approximately due north. 

Agonic*. — Pertaining to the Agone. 



14 



A DICTIONARY OF ELECTRICAL 




Air-Bla§t.— An invention of Prof. Elihu Thomson to pre- 
vent the injurious action of destructive sparking at the com- 
mutator of a dynamo-electric machine. 

A thin, forcible blast of air is delivered through suitable 
tubes at points on the three-part commutator cylinder of the 
Thomson Houston dynamo, where the collecting- brushes 
bear on its surface. The effect is 
to blow out the arc and thus pre- 
vent lis destructive action on the 
commutator segments. The use of 
the air-blast also permits the free 
application of oil. thus further avoid- 
ing wear. 

The blast-nozzles are shown at 
B 3 , B 3 , Fig. 8, near the collecting 
brushes. 
The air-supply is ob- 
tained from a centri- 
fugal blower attached 
directly to the shaft of 
the machine. Its con- 
struction and operation 
will be readily under- 
stood from an inspec- 
tion of Fig. 9, in which 
the top is removed for 
a ready examination of 
the interior parts. 

Fig, 0. 

Alarms, Electric Various automatic devices by 

which attention is called to the occurrence of certain events, 
such as the opening of a door or window; the stepping of a 
person on a mat or staircase ; the rise or fall of temperature 
bej^ond a given predetermined point ; or to call a person to a 
telegraphic or telephonic instrument. 




WORDS, TERMS AND PHRASES. 



15 



Electric alarms arc operated by either the closing or the 
opening of an electric circuit, generally the former, by means 
of which an electro-magnetic or 

Electric alarms may be di- 



vided into two classes, viz. : 

1. Mechanically operated 
alarms, or those operated by 
clock-work, that is started by 
means of an electric current. 

2. Those in which the alarm 
is both set into operation and 
operated by the action of an 
electric current. 

In Fig. 10, is shown the 
general construction of an 
electrically started mechani- 
cal alarm. The attraction of 
the armature B, by the electro- 
magnet A, moves the arma- 
ture lever pivoted at C, and 
thus releases the catch e, and 
permits the spring or weight 
connected with the 
strike the bell. 

Electrically actuated alarm-bells 
automatic make-and-break form, 
operated by the attraction of the 



mechanical bell is rum 

itlF 1 




Fig. 10. 
clock movement to set it in motion and 



are generally of the 
The striking lever is 
armature of an electro- 
magnet, and is provided with a contact-point, so placed that 
when the hammer is drawn away from the bell, on the 
electro-magnet losing its magnetism, the contact-point is 
closed, but when it is drawn towards the bell the contact is 
opened. When, therefore, the hammer strikes the bell, 
the circuit is opened, and the electro-magnet releases its 
armature, permitting a spring to again close the contact by 
moving the striking lever away from the bell. Once set into 



16 



A DICTIONARY OF ELECTRICAL 



action, these movements are repeated while there is battery 
power sufficient to energize the magnet. 
T 

In Fig. 11, the 

battery terminals 

are connected 
with the right and 
left hand binding- 
posts, P and M. 
The hammer K, is 
connected with a 
striking lever, 
which forms part 
of the circuit, and 
which is attached 
to the armature 
o f the electro- 
Fig. n. magnet e. A me- 

tallic spring g, bears against the armature when the latter 
is away from the magnet, but does not touch the armature 
when it is moved towards the magnet. The movements of 
the armature thus automatically open and close the circuit 
of the electro-magnet. 

This form of make-and-break is called an automatic make- 
and-break. 

Alarms, Electric Burglar 




An electric device 

to automatically announce the opening of a door, window, 
closet, drawer, or safe, or the passage of a person through 
a hallway, or on a stairway. 

Electric burglar alarm devices generally consist in mechan- 
ism for the operation of an automatic make-and-break bell 
on the closing of an electric circuit. The bell may either 
continue ringing only while the contact remains closed, or, 
may, by the throwing on of a local circuit or battery, con- 
tinue ringing until stopped by some non-automatic device, 
such as a hand-switch. 



WORDS, TERMS AND PHRASES. 



17 



The alarm-bell is stationed either in the house when occu- 
pied, or on the outside when the house is temporarily vacated, 
or may connect directly with the nearest police station. 

Burglar-alarm apparatus is of a variety 
of forms. Generally, devices are provided 
by moans of which, in case of house pro- 
tection, an annunciator shows the exact 
part where an entrance has been at- 
tempted. (See Annunciator.) Switches 
are provided for disconnecting all or parts 
of the house from the alarm when so de- 
sired, as well as to permit windows to be 
partly raised for purposes of ventilation 
without sounding the alarm. A clock' is 
frequently connected with the alarm for 
the purpose of automatically disconnecting any portion of 
the house at or for certain intervals of time. 

Fig. 12, shows a burglar alarm with annunciator, switches, 
switch-key, cut-oil, and clock. 




Fig. 12. 



A I sir ins, Electric Burglnr- 



-Yalc Lock 



Switch lor. — An alarm whereby the opening of a door by 
an authorized party provided with the regular key will not 
sound an alarm, but any other opening will sound such alarm. 

Alarm§, Electric Fire or Temperature In- 
struments for automatically sounding an alarm on an increase 
of temperature beyond a certain predetermined point. 

Fire-alarms are operated by thermostats, or by means of 
mercurial contacts; i. e., a contact closed by the expansion of a 
column of mercury. (See T 'her most 'at.) 

In systems of fire-alarm telegraphs, the alarm is automati- 
cally sounded in a central police station and in the district 
fire-engine house. (See Telegraphy, Fire-alarm.) 

The action of mercurial contacts is dependent on the fact 
that, as the mercury expands hy the action of the heat, it 
reaches a contact-point placed in the tube and thus completes 



18 A DICTIONARY OF ELECTRICAL 

the circuit through its own mass, which forms the other or 
movable contact. Sometimes both contacts are placed on 
opposite sides of a tube and are closed when the mercury 
reaches them. 

Mercurial-temperature or thermostat alarms are employed 
in hot-houses, incubators, tanks, and buildings, for the 
purpose of maintaining a uniform temperature. 

Alarms, Electric Water or Liquid Level 

Devices for sounding an alarm electrically when a water sur- 
face varies materially from a given level. 

An electric bell is placed in a circuit that is automatically 
closed or broken by the movement of contact-points operated 
by a change of liquid level. 

Alarms, Telegraphic Alarm bells for calling 

the attention of an operator to a telegraphic instrument when 
the latter is of the non-acoustic or needle type. 

In acoustic systems of telegraphy, the sounds themselves 
are generally sufficient for this purpose. 

Alarms, Telephonic An alarm-bell for calling 

a correspondent to the telephone. 

These alarms generally consist of magneto-electric bells. 
(See Magneto-Electric Call-Bell) 

Alcohol, Electrical Rectification of. A 

process whereby the bad taste and odor of alcohol, due to the 
presence of aldehydes, are removed by the electrical con- 
version of the aldehydes into true alcohols through the ad- 
dition of Ivydrogen atoms. 

An electric current sent through the liquid, between zinc 
electrodes, liberates oxygen and hydrogen from the decom- 
position of the water. The hydrogen converts the aldehydes 
into alcohol, and deprives the products of their fusel oil, 
while the ox}'gen forms insoluble zinc oxide. 
Algebraic dotation.— (See Notation, Algebraic.) 

Alphabet, Telegraphic —An arbitrary code 

consisting of dots and dashes, sounds, deflections of a mag- 



WORDS, TERMS AND PHRASES. 19 

netic needle, flashes of light, or movements of levers, follow- 
ing- one another in a given predetermined order, to represent 
the letters of the alphabet and the numerals. 

Alphabet, Morse's Telegraphic 

Various groupings of dots and dashes, or deflections of a 
magnetic needle to the right and left, that represent the letters 
of t lie alphabet or other signs. 

In the Morse alphabet dots and dashes are employed in 
recording systems, and sounds of varying- lengths, correspond- 
ing to the dots and dashes in the sounder system. 
American Morse Code, 
alphabet. 

a n 

b o - - 

c - - - p 

d --- q 

e - r - - • 

f s --- 

g t - 

h u 

i - - v 

k x 

1 y 

m z — - 

& - --- 

NUMERALS. 

1 

9. 7 



3 8 — - 

4 9 — - 

5 

PUNCTUATION marks. 

Period Interrogation 

Comma Exclamation 



20 A DICTIONARY OF ELECTRICAL 

Iii the needle telegraph, the code is similar to that used in 
the Morse Alphabet. (.See Telegraphy, Single-needle.) 

Alphabet, Telegraphic: Continental Code. 





Single 




Single 


Printing 


Needle 


Printing 


Needle 


a 


s/ 


n 


A 


b 


A* 


o 


/// 


c 


AA 


p . 


nAs 


d 


A 


q 


/A/ 


e . 


\ 


r 


sA 


f 


vsA 


s ... 


W\ 


g 


/A 


t 


/ 


h .... 


WW 


U .. 


ss/ 


i 


w 


V ... 


wn/ 


j 


■,/// 


w 


sA 


k 


A/ 


X __ .. 


/sv/ 


1 


nAn 


y 


A A 


m : 


A 


Z 


ANS 



Similar symhols are emploj r ed for the numerals and the 
punctuation marks. 

It will be observed that it is mainly in the characters of the 
American Morse, in which spaces are used, that the Conti- 
nental characters differ from the American. This is due to 
the use of the needle instrument. A movement or deflection 
of the needle to the left signifies a dot; a movement to the 
right, a dash. 

For methods of receiving the alphabet, see Sounder, Morse 



WORDS, TERMS AND PHRASES. 21 

Telegraphic. Recorder, Morse's. Recorder, Chemical. Re- 
corder, Siphon. Relay or Receiving Magnet. 

All-night Arc Lump. — (See Double-Carbon Arc Lamp.) 

Alloy. — A combination, or mixture, of two or more metallic 
substances. 

Alloys in most cases appear to be true chemical compounds. 
In a few instances, however, they may form simple mixtures. 

The composition of a few important alloys is here given : 

Solder, plumber's ; Tin GO parts, Lead 31 parts. 

Pewter, hard ; Tin 92 parts, Lead 8 parts. 

Britannia metal ; Tin 100 parts, Antimony 8 parts, Copper 4 
parts, Bismuth 1 part. 

German silver ; Copper 50, Zinc 25, Nickel 25 parts. 

Type metal ; Lead 80, Antimony 20 parts. 

Brass, white ; Copper 65, Zinc 35 parts. 

Brass, red ; Copper 00, Zinc 10 parts. 

Speculum metal ; Copper 07, Tin 33 parts. 

Bell metal ; Copper 78, Tin 22 parts. 

Aluminium bronze; Copper 90, Aluminium 10 parts. 

Alloys, Palladium (See Palladium Alloys.) 

Allotropy, Allotropic Stale.— A modification of a 
substance, in which, without changing its chemical compo- 
sition, it assumes a condition in which its physical and chem- 
ical properties are distinct from those it ordinarily possesses. 

Thus the element carbon occurs in three widely different 
allotropic states, viz.: 

(1) As charcoal, or ordinary carbon ; 

(2) As graphite, or plumbago ; and 

(3) As the diamond, 

Alternating Current. — An electric current that alter- 
nately tlows in opposite directions. (.See Current, Alterna- 
ting.) 

Alternating Motor. — (See Motor, Alternating Cur- 
rent.) 



22 A DICTIONARY OF ELECTRICAL 

Alternating Dynamo-Electric Machine.— A dy- 
namo-electric machine that furnishes alternating- currents, 
(See Dynamo-Electric Machine. ) 

Alternating System of Distribution.— A system of 
electric distribution in which lamps, motors, or other electro- 
receptive devices are operated by means of alternating- cur- 
rents that are sent over the line, but which, before passing 
through said devices, are modified by apparatus called con- 
verters or transformers. (See Converter or Transformer.) 

For details of the alternating system of distribution, see 
Systems of Distribution by Alternating Currents. 

Alternatives, Voltaic A term used in medical 

electricity to indicate sudden reversals of polarity of the elec- 
trodes of a voltaic battery. 

An alternating current from a voltaic battery, obtained by 
tin 1 use of i suitable commutator. 

Sudden reversals of polarity produce more energetic effects 
of muscular contraction than do simple closures or comple- 
tions of the circuit. 

Since all electricity is one and the same thing or force, what- 
ever its source, the necessity for the term voltaic alternative 
in place of alternating current is by no means clear. The 
only consideration that would appear to warrant its con- 
tinued use is that the alternating currents obtained from 
the voltaic batteries generally employed in electro thera- 
peutics, by the action of a pole-changer, possess a much 
smaller electro-motive force than do faradic currents, which 
are also alternating. 

Amalgam. — The combination or mixture of a metal with 
mercury. 

Amalgam, Electric A substance with which 

the rubbers of the ordinary frictional electric machines are 
covered. 

Electric amalgams are of various compositions. The fol- 
lowing is excellent : 



WORDS, TERMS AND PHRASES. 23 

Melt together five parts of zinc and three of tin, and gradu- 
ally pour the niolten metal into nine parts of mercury. 
Shake the mixture until cold, and reduce to a powder in 
a warm mortar. Apply to the cushion by means of a thin 
layer of stiff grease. 

Mosaic gold, or bisulphide of tin, and powdered graphite, 
both act as good electric amalgams. 

An electric amalgam not only acts as a conductor to carry 
off the negative electricity, but being highly negative to the 
glass, produces a far higher electrification than would leather 
or chamois. 

Amalgamation. — The act of forming an amalgam, or 
effecting the combination of a metal with mercury. 

Amalgamation of* Zinc Battery Plates. — Cover- 
ing the surface of the zinc plate of a voltaic cell with a thin 
layer of amalgam in order to avoid local action. (See Action, 
Local. ) 

For details of process, see Zinc, Amalgamation of. 

Amber. — A resinous substance, generally of a transparent, 
yellow color. 

Amber is interesting electrically as being believed to be the 
substance in which the properties of electric attractions and 
repulsions imparted by friction or rubbing were first noticed. 
It was called by the Greeks rfXeicTpov from which the word 
electricity is derived. This property was mentioned by the 
Greek, Thales of Miletus, 600 B. c, as well as by Theophrastus. 

Amorphous. — Having no definite crystalline form. 

Mineral substances have certain crystalline forms, that 
are as characteristic of them as are the forms of animals or 
plants. Under certain circumstances, however, they occur 
without definite crystalline form, and are then said to be amor- 
phous solids. 

Ampere. — The practical unit of electric current. 

Such a current (or rate of flow or transmission of electricity) 



24 A DICTIONARY OF ELECTRICAL 

as would pass with an E. M. F. of one volt through a circuit 
whose resistance is equal to one ohm. That is to say, a cur- 
rent of the definite strength that would How through a circuit 
of a certain resistance and with a certain electro-motive 
force. (See Electro-Motive Force. Volt. Resistance. Ohm.) 

Since the ohm is the practical unit of resistance, and the volt 
the practical unit of electro-motive force, the ampere, or the 
practical unit of current, is the current that would flow against 
unit resistance, under unit pressure or electro-motive force. 

To make this clearer, take the analogy of water flowing 
through a pipe under the pressure of a column of water. That 
which causes the flow is the pressure or head ; that which 
resists the flow is the friction of the pipe, winch will vary 
with a number of circumstances. The rate of flow may he 
represented by so many cubic inches of water per second. 

As the pressure or head increases, the flow increases pro- 
portionally ; as the resistance increases, the flow diminishes. 

Electrically, electro-motive force corresponds to the pres- 
sure or head of the water, and resistance to the friction of the 
water and the pipe. The ampere, which is the unit rate of 
flow per second, may therefore be represented as follows, 

E 
viz.: c = — , as was announced by Ohm in his law. (See 
R 

Ohm's Laic.) 

This expression signifies that C, the current in amperes, is 
equal to E, the electro-motive force in volts, divided by R, the 
resistance in ohms. 

We measure the rate of flow of liquids as so many cubic 
inches or cubic feet per second — that is, in units of quantity. 
We measure the rate of How of electricity as so much elec- 
tricity per second. The electrical unit of quantity is called the 
Coidomb. (See Coidomb.) The coulomb is such a quantity 
as would pass in one second through a circuit in which the 
rate of flow is one ampere. 



WORDS, TERMS AND PHRASES. 25 

An ampere per second is therefore equal to one coulomb. 

The electro-magnetic unit of current is such a current that, 
passed through a conducting wire bent into a circle of the 
radius of one centimetre, would attract a unit magnetic pole 
held at its centre, and sufficiently long to practically remove 
the other pole from the influence, with unit force, i.e., the 
force of one dyne. (See Dyne.) The ampere, or practical 
electro-magnetic unit, is one-tenth of such a current ; or, in 
other words, the absolute unit of current is ten amperes. 

An ampere may also be defined by the chemical decom- 
position the current can effect as measured by the quantity 
of hydrogen liberated, or metal deposited. 

Delined in this way, an ampere is such a current as will 
deposit .00032959 grammes, or .005084 grains, of copper per 
second on the plate of a copper voltameter (See Voltameter), 
or winch will decompose .00009336 grammes, or .001439 
grains, of dilute sulphuric acid per second, or pine sulphuric 
acid at 50' F. diluted with about Qfteen percent, of water, that 
is, dilute sulphuric acid of Sp. Gr. of about 1.1. 

Impc i < -iloin . Ampere-Minute, Ampere-See- 
ond. — One ampere flowing for one hour, one minute, or one 
second respectively. 

The ampere-hour is in reality a unit of quantity like the 
coulomb. It is used in the service of electric currents, and 
is equal to the product of the current delivered, by the time 
during which it is delivered. The ampere-hour is not a meas- 
ure of energy, but when combined with the volt, and ex- 
pressed in watt-hours, it is a measure of energy. 

The storing capacity of accumulators is generally given in 
ampere-hours. The same is true of primary batteries. 

One coulomb = .0002778 ampere-hours. 

One ampere-hour = 3,600 coidombs. (See Watt-Hour, Watt- 
Minute, Watt-Second.) 

Ampere-Meter; Am-meter. — A form of galvanometer 
originally designed by Ayrton and Perry to indicate directly, 



26 



A DICTIONARY OF ELECTRICAL 



the strength of current passing in amperes. (See Galvano- 
meter.) 

Like all galvanometers, the strength of current passing, 
i. e., the number of amperes, is indicated by the deflection of a 
magnetic needle placed inside or over a coil of insulated wire 
through which the current to be measured is passed. 

In the form originally devised by Ayrton and Perry, the 
needle came to rest almost immediately, or was dead beat in 
action. (See Dead Beat.) It moved through the field of a 
permanent magnet. The instrument was furnished with a 
number of coils of insulated wire, which could be connected 
either in series or in multiple-arc by means of a commutator, 
thus permitting the scale reading to be verified or calibrated 
by the use of a single voltaic cell. (See Circuits, Varieties 
of. Commutator. Calibration, Absolute or Relative, of Instru- 
ment.) In this case the coils were turned to series, and the 
plug to the left pulled out, thus introducing a resistance of 
one ohm. 

Q Fig. 13, represents a form 

of Ayrton and Perry's Am- 
meter. A device called a 
commutator for connect- 
ing the coils either in series 
or parallel is shown at C. 
Binding-posts are provided 
at P, PS, and S. The dy- 
namo terminals are con- 
nected at the posts P, P, 
and the current will pass 
only when the coils are 
in multiple, thus avoiding accidental burning of the coils. 
In this case the entire current to be measured passes through 
the coils so coupled. The posts S, and PS are for connect- 
ing the single battery cell current. 
A great variety of ampere-meters, or am-meters, have been 




Fig. 13. 



WORDS, TERMS AND PHRASES. 27 

devised. They are nearly all, however, constructed on es- 
sentially the same general principles. 

Ampere-Feet. — The product of the current in amperes 
by the distance in feet through which that current passes. 

It has been suggested that the term ampere-feet should be 
employed in expressing- the strength of electro-magnetism, 
in the field magnets of dynamo-electric machines or other 
similar apparatus. 

Ampere-Turns, or Ampere- Win dings. — A single 
turn or winding through which one ampere passes. 

The number of amperes multiplied by the number of wind- 
ings or turns of wire in a eoil give the total number of am- 
pere-turns in the coil. The magnetism developed by a given 
number of ampere-turns is independent of the current or of 
the number of turns of wire, as Jong as the product of the 
amperes and the turns remains the same. That is to say, the 
same amount of magnetism can be obtained by the use of many 
windings and a small current, as in shunt dynamos, or by a 
few turns and a proportionally large current, as in series 
dynamos. (See Dynamo-Electric Machines.) 

Amperc-Voll. — A watt, or -.},, of a horse-power. 

This term is generally written volt-ampere. (See Volt-Am- 
pere.) 

Amperian Currents.— The electric currents that are 
assumed in the Ampenan theory of magnetism to How around 
the molecules of a magnet. (See Magnetism, Amperian 
Theory or Hypothesis of.) 

The Ampenan currents are to be distinguished from the 
Eddy, Foucault, or Parasitical Currents, since, unlike them, 
they are directed so as to produce useful effects. (Sec Cur- 
rents, Eddy, Foucault, Parasitical.) 

Amplitude of Vibration or Wave.— The ratio that 
exists in any sound-wave between the degree of condensation 
and rarefaction of the air or other medium in which the wave 
is propagated. 



28 A DICTIONARY OF ELECTRICAL 

The amplitude of a wave is dependent on the amount of 
energy charged on the medium in which the vibration or wave 
is produced. 

A vibration or wave is a to-and-fro motion produced in an 
elastic material or medium by the action thereon of energy. 
Sound, light and heat are effects produced by the action of 
vibrations or waves, which, in the case of sound, are set up 
in the air, and, in that of light and heat, in a highly tenuous 
medium called the luminiferous ether. 

As the amplitude of a sound wave increases, the loudness 
or intensity of the sound increases. As the amplitude of the 
ether-wave increases, the brilliancy of the light or the inten- 
sity of the heat increases. 

Let AC, Fig. 14, represent an elastic cord or string tightly 
stretched between A and C. It' the string be plucked by the 
finger, it will move to and fro, as shown by the dotted fines. 
Each to-and-fro motion is called a vibration. The vertical 



*<: 



B ^^C 



E 
Fig. Ik. 

distance B D, or B E, represents the amplitude of the 
vibration, and the sound produced is louder, the greater the 
amount of energy with which the string has been plucked, 
or, in other words, the greater the value of B D, or B E. 

Vibrations assume various forms in solid or fluid media, but 
in all cases the amplitude will be proportional to the amount 
of energy that causes the vibration. 

Analogous Pole.— (See Pole, Analogous.) 

Analysis.— The determination of the composition of a 
compound substance by separating it into the simple sub- 
stances of which it is composed. 

Chemical analysis is qualitative when it simply ascertains 



WORDS, TERMS AND PHRASES. 29 

the kinds of elementary substances present. It is quanti- 
tative when it ascertains the relative proportions in which the 
different components enter into the compound. 

Analysis, Electric Ascertaining the composi- 
tion of a substance by electrical means. 

Various processes have been proposed for electric analysis ; 
they consist essentially in decomposing the substance by 
means of electric currents, and are either qualitative or 
quantitative. (See Electrolysis, or Electrolytic Decomposi- 
tion,) 

An elect rot on us. — In electro therapeutics, the decreased 
functional activity that occurs in a nerve in the neighbor- 
hood of the anode, or positive electrode. (See Electro- 
tonus.) 

Angle. — The deviation in direction between two lines. 

Angles are measured by arcs of cir- 
cles. The angle at B A C, Fig. 15, is the 
deviation of the straight line A B from 
A C. In reading the lettering of an 
angle the letter placed in the middle 
indicates the angle referred to. Tims 
B A C, means the angle between AB ^ . 

and AC; BAD, the angle between 

B A and A D. Angles are valued in degrees, there being 360 
degrees in an entire circumference or circle. Degrees are 
indicated thus : 90°, or ninety degrees. 

The complement of an angle is what the angle needs to 
make its value 90°, or a right angle. Thus B A E, is the 
complement of the angle E A D, since BAE + EADr= 90°. 

The supplement of an angle is what the angle needs to make 
its value 180°, or two right angles. Thus E AC is the supple- 
ment of E A D, because EA D|EAC= 180°, or two right 
angles. 

Angle of Declination or Variation.— The angle 




30 



A DICTIONARY OF ELECTRICAL 




Fig. 16. 



which measures the deviation of the magnetic needle from 
the east or west of the true geographical north. 

Thus, in Fig. 16, if N S represents the 
true north and south line, the angle of 
declination is N O A, and the sign of the 
variation is east, because the deviation of 
the needle is toward the east. For f u ether 
details see Declination or Variation of 
Magnetic Needle. 

Angle of I>ip or Inclination.— 

The angle which a magnetic needle, free 
to move in a vertical and horizontal 
plane, makes with a horizontal line passing through its point 
of support. 

A magnetic needle supported at its centre of gravity, and 
capable of moving freely in a vertical as well as in a horizontal 
plane, does not retain a horizontal position at all parts of the 
earth's surface. 

The angle which marks its deviation from the horizontal 
position is called the angle of dip or inclination. For further 
details see Dip, Magnetic. 

Angle of Lag. — The angle through which the axis of 
magnetism of the armature of a dynamo-electric machine is 
shifted by reason of the resistance its core offers to sudden 
reversals of magnetization. 

A bi-polar armature of a dynamo-electric machine, has its 
magnetism reversed twice in every rotation. The iron of the 
core resists this magnetic reversal. The result of this resist- 
ance is to shift the axis of magnetization in the direction of 
rotation. The angle through which the axis has thereby been 
shifted is called the angle of lag. This term, angle of lag, is 
sometimes incorrectly applied so as to include a similar result 
produced by the magnetization due to the armature current 
itself. It is this latter action which, in armatures with soft 



WORDS, TERMS AND PHRASES. 31 

non cores, is the main cause of the angle of lead. (See Angle 
of Lead. Lead of Brushes.) 

Angle of Lead. — The angular deviation from the normal 
position which must be given to the collecting brushes on the 
commutator cylinder of a dynamo-electric machine, in order 
to avoid destructive binning. (See Burning at Commutator.) 

The necessity for giving the collecting* brushes a lead, arises 
both from the magnetic lag, and the distortion of the field 
of the machine by the magnetization of the armature current. 
The angle of lead is, therefore, equal to the sum of the angle 
of lag and the angular distortion due to the magnetization 
produced by the armature current. 

Angular Velocity. — The velocity of a body moving in a 
circular path, measured, not, as usual, by the length of its 
path divided by the time, but by the angle that path subtends 
times the length of the radius, divided by the time. 

If f* is the radius, a the angle, and t the time, then 

ra 
Angular Velocity = — . 
t 

Unit Angle is that angle subtended by a part of the circum- 
ference equal to the length of the radius, or 57° 17' 44". 8 nearly 
(Daniell). 

Unix Angular Velocity is the velocity under which a particle 
moving in a circular path whose radius equals unity would 
traverse unit angle in unit time. 

Animal Electricity. — Electricity produced during life in 
the bodies of certain animals, such as the Torpedo, the Gym- 
notus, and the Silurus. 

Some of these animals, when of full size, are able to give 
very severe shocks, and use this curious power as a means of 
defence against their enemies. 

All animals probably produce electricity. If the spinal cord 
of a recently killed frog be brought into contact with the 
muscles of the thigh, a contraction will ensue (Matteucci). 



32 A DICTIONARY OF ELECTRICAL 

The nerve and muscle of a frog, connected by a water con- 
tact with a sufficiently delicate galvanometer, show the 
presence of a current that may last several hours. Du Bois- 
Reymond showed that the ends of a section of muscular 
fibres are negative, and their sides positive, and has obtained 
a current by suitably connecting them. 

All muscular contractions apparently produce electric cur- 
rents. 

Anion. — The electro-negative radical of a molecule. 

Literally, the term ion signifies a group of wandering atoms. 
An anion is that group of atoms of an electrically decomposed 
or electrolysed molecule which appears at the anode. (See 
Electrolysis. Anode ) 

As the anode is connected with the electro-positive termi- 
nal of a battery or source, the anion is the electro-negative 
radical or group of atoms, and therefore appears at the electro- 
positive terminal. A kathion, or electro-positive radical, ap- 
pears at the kathode, which is connected with the electro- 
negative terminal of the battery. Oxygen and chlorine are 
anions. Hydrogen and the metals are kathions. 

Anisotropic Conductor.— A conductor which, though 
homogeneous in structure like crystalline bodies, has different 
physical properties in different directions, just as crystals 
have different properties in the direction of the different 
crystalline axes. 

Anisotropic conductors possess different powers of electric 
conduction in different directions. They differ in this respect 
from isotrojric conductors. (See Isotropic Conductor.) 

Anisotropic Medium. — A medium, homogeneous in 
structure like crystalline bodies, possessing different powers 
of specific inductive capacity in different directions. 

The term is used to distinguish it from an isotropic medium. 
(See Isotropic Medium.) 

Anode — The conductor or plate of a decomposition cell 



WORDS, TERMS AND PHRASES. 33 

connected with the positive terminal of a batteiy, or other 
electric source. 

That terminal of an electric source out of which the current 
flows into the liquid of a decomposition cell or voltameter is 
called the anode. That terminal of an electric source into 
which the current flows from a decomposition cell or volta- 
meter is called the kathode, 

The anode is connected with the carbon or positive ter- 
minal of a voltaic battery, and the kathode with the zinc, or 
negative terminal. Therefore the word anode has been used 
to signify the positive terminal of an electric source, and 
kathode, the negative terminal, and in this sense is employed 
generally in electro therapeutics. It is preferable, however, 
to restrict the Avords anode and kathode to those terminals of 
a source at which electrolysis is taking place. 

The terms anode and kathode in reality refer to the electro- 
receptive devices through which the current flows. Since it 
is assumed that the current flows out of a source from its 
positive pole or terminal, and back to the source at its nega- 
tive pole or terminal, that pole of any device connected with 
the positive pole of a source is the part by or at which the 
current enters, and that connected with the negative pole, the 
part at which it leaves. Hence, probably, the change in the 
use of the words already referred to. 

Since the anion, or the electro-negative radical, appears at 
the anode, it is the anode of an electro-plating bath, or the 
plate connected with the positive terminal of the source that 
is dissolved. 

When the term anode was first proposed by Faraday, vol- 
taic batteries were the only available electric source, and 
the term referred only to the positive terminal of a voltaic 
battery when placed in an electrolyte. 

Anodic Opening Contraction.— The muscular con- 
traction observed on the opening of a voltaic circuit, the 
anode of which is placed over a nerve, and the kathode at some 
other part of the body. 



34 



A DICTIONARY OF ELECTRICAL 



This term is generally written A. O. C. When the anode 
is placed over a nerve and a weak current is employed, if the 
circuit be kept closed for a few minutes, it will be noticed 
that, on opening, the contraction will be much greater than 
if it had been opened after being closed for only a few seconds. 
The effect of the A. O. C. therefore depends not only on the 



rent has passed through the nerve. 

Annunciator, Electro-Magnetic An electric 

device for automatically indicating the places at which one or 
more electric contacts have been closed. 

Annunciators are employed for a variety of purposes. In 
hotels they are used for indicating the number of a room the 
occupant of which desires some service which he signifies by 
pushing a button, thus closing an electric circuit. This is in- 
dicated or announced on the annunciator by the falling of a 

drop on which is printed a 
number corresponding with the 
room, and the ringing of a bell 
to notify the attendant. The 
number is released by the action 
of the armature of an electro- 
magnet. The drops are replaced 
in their former position by some 
mechanical device operated by 
the hand. In the place of a drop 
a needle is sometimes used, 
which points to the number sig- 
nalling, by the attraction of the 
armature of an electro-magnet. 
Annunciators for houses, bur- 
glar-alarms, fire-alarms, eleva- 
tors, etc., are of the same general 
construction. 
Fig. 17, shows an annunciator suitable for use in hotels. 




WORDS, TERMS AND PHRASES. 35 

The numbers 28 and 85 are represented as having been 
dropped by the closing of the circuit connected with them. 

Anomalous Magnet. — A magnet possessing more than 
two free poles. 

There is no such thing as a unipolar magnet. All magnets 
have two poles. Sometimes, however, several magnets are 
so grouped that there appear to be more than two poles in the 
same magnet. 




Fig. 18. 

Thus, in Fig. 18, the magnet ABC appears to possess 
three poles, two positive poles at A and C, and a central 
negative pole at B. 

It is clear, however, that the central pole is in reality formed 
of two juxtaposed negative poles, and that ABC actually 
consists of two magnets with two poles to each. 




A B 



Fig. 19. 

The magnet A B C D, Fig. 19, which in like manner ap- 
pears to possess four separate poles, in reality is formed of 
three magnets with two poles to each. 

Since unlike magnetic poles neutralize each other, it is clear 
that only similar poles can thus be placed together in order to 
produce additional magnet poles. 




36 A DICTIONARY OF ELECTRICAL 

The six-pointed star shown 
in Fig. 20, is an anomalous 
magnet with apparently seven 
poles. The formation of the 
central N-pole, as is evident 
5 from an inspection of the 
drawing, is due to the six 
separate north poles, n, n, n, 
n, n, n, of the six separate 
magnets Sn, Sn, etc. Such 
a magnet would be formed 
by touching the star at the 
point N with the S-pole of a sufficiently powerful magnet. 

These extra poles are sometimes called consequent poles. 
Their presence may be shown by means of a compass needle, 
or by rolling the magnet in iron filings, which collect on the 
poles. 

Anti-Induction Conductor. — A conductor so con- 
structed as to avoid injurious inductive effects from neighbor- 
ing telegraphic or electric light and power circuits. 

Such anti-induction conductors generally consist of a con- 
ductor and a metallic shield surrounding the conductor, which 
is supposed to prevent induction taking place in the wire itself. 
The anti-induction conductor sometimes consists of a con- 
ductor enclosed by some form of metallic shield, which is 
supposed to prevent the action of electrostatic induction. 
Antilogous Pole— (See Pole, Antilogous.) 
Anvil. — The front contact of a telegraphic key that limits 
its motion in one direction. (See Telegraphic Key.) 

A. O. C— A contraction used in medical electricity for 
Anodic Opening Contraction. (See Anodic Opening Con- 
traction.) 

Apparatus, I utcrlockin? (See Interlocking 

Apparatus Block System for Railroads.) 



WORDS, TERMS AND PHRASES. 37 

Arago'§ Disc. — (See Disc, Arago's.) 

Arc Lamp, Electric (See Lamp, Arc, Electric.) 

Arc, Metallic A voltaic arc formed between me- 
tallic electrodes. 

When the voltaic arc is formed between metallic electrodes 
instead of carbon electrodes, a flaming arc is obtained, the color 
of which is characteristic of the burning metal ; thus copper 
forms a brilliant green arc. The metallic arc, as a rule, is 
much longer than an arc with the same current taken between 
carbon electrodes. 

Arc Micrometer. — (See Micrometer, Arc.) 

Arc, Voltaic The brilliant arc or bow of light 

that appears between the carbon electrodes or terminals of a 
sufficiently powerful source of electricity. 

The source of light in the electric arc lamp. 

It is called the voltaic arc because it was first obtained by 
the use of the battery invented by Volta. The term arc was 
given to it from the shape of the luminous bow or arc formed 
between the carbons. 

To form the voltaic arc the carbon electrodes are first placed 
in contact and then gradually separated. A brilliant arc of 
flame is fonned between them, which consists mainly of vola- 
tilized carbon. The electrodes are therefore consumed, first, 
by actual combination with the oxygen of the air, and, second, 
by volatilization under the combined influence of the electric 
current and the intense heat. 

As a result of the formation of the arc, a tiny crater is formed 
in the end of the positive carbon, and appears to mark the 
point out of which the greater part of the current flows. 

The crater is due to the greater volatilization of the elect- 
rode at this point than elsewhere. It marks the position of 
greatest temperature of the electrodes, and is the main source 
of the light of the arc. When, therefore, the voltaic arc is 
employed for the purposes of illumination with vertically op- 



38 A DICTIONARY OF FXECTRICAL 

posed carbons, the positive carbon should be made the upper 
carbon, so that the focus of greatest intensity of the light may 
be favorably situated for illumination of the space below the 
lamp. 

The crater in the end of the positive 
carbon is seen in Fig-. 21. On the 
opposed end of the negative carbon 
a projection or nipple is formed by 
the deposit of the electrically volatil- 
ized carbon. The rounded masses or 
globules that appear on the surface 
of the electrodes are due to deposits 
of molten foreign matters in the car- 
bon. 

The carbon, both of the crater and 
its opposed nipple, is converted into 
pure, soft graphite. 

Arc, Voltaic Resistance 

of. — The resistance offered by the voltaic arc to the passage 
of the current. 

Like all conductors, the ohmic resistance of the arc increases 
with its length, and decreases with its area of cross-section. 
An increase of temperature decreases the resistance of the 
voltaic arc. 

The total apparent resistance of the voltaic arc is composed 
of two parts, viz. : 

(1.) The true ohmic resistance. (See Ohmic or True Resist- 
ance.) 

(2.) The counter electro-motive force, or spurious resistance. 
(See Spurious Resistance.) 

Areometer or Hydrometer— An instrument for de- 
terming the specific gravity of a liquid. 

A common form of hydrometer consists, as shown in Fig. 
22, of a closed glass tube, provided with a bulb, and filled at 
the lower end with mercury or shot. When placed in different 




WORDS, TERMS AND PHRASES. 



39 



so liquids, it floats with part of the tube out of the liquid. 

The lighter the liquid the smaller is the portion that 
': 50 remains out of the liquid when the instrument floats. 

The specific gravity is determined by observing the 
iQ depth to which it sinks when placed in different liquids, 

as compared with the depth it sinks when placed in 
30 water. 

Argaiul Lighter, Electric An electric 

20 device for lighting the gas by pulling a pendant B, 
Fig. 23, after it is turned on by hand. 

The gas is ignited by means of an electric spark 
obtained from the extra current of a spark coil. (See 
Current, Extra). 

9 

Argaml Valve Burner, 

Electric A burner in 

which the pulling of the ball B, 
Fig. 24, turns on and lights the 
FtgTss. gas, while the motion of the slide 
extinguishes it. 

In some forms of 
argand burner, a| 
second pulling of the 
ball B, turns off the 
gas. 

^ Armature. — A 

mass of iron or other 
magnetizable materi- 
al placed on or near 
the pole or poles of a p ig% ^ 

Fig. 23. magnet. 

In the case of a permanent magnet the armature, when 
used as a keeper, is of soft iron and is placed directly on the 
magnet poles. In this case it preserves or keeps the 
magnetism by closing the lines of magnetic force of the 





40 A DICTIONARY OF ELECTRICAL 

magnet through the soft iron of the armature, and is then 
called a keeper. In the case of an electro-magnet, the arma- 
ture is placed near the poles, and is moved toward them 
whenever the magnet is energized by the passage of the cur- 
rent. This movement is made against the action of a spring 
or weights, so that on the loss of magnetism by the magnet, 
the armature moves in the opposite direction. (See Magnet, 
Permanent. Keeper of Magnet.) 

When the armature is of soft iron it moves towards the 
magnet on the completion of the circuit through the coils, no 
matter in what direction the current flows, and is then called 
a non-polarized armature. When made of steel, or of another 
electro-magnet, it moves towards or from the poles, according 
to whether its poles are of the same or of different polarity. 
Such an armature is called a. polarized armature. (See Arm- 
ature, Polarized.) 

Armature, Dynamo The part of a dynamo- 
electric machine in which the useful currents are gene- 
rated. 

The armature usually consists of a series of coils of insu- 
lated wire or conductors, that are wrapped around or grouped 
on a central core of iron. The movement of these wires or 
conductors through the magnetic field of the machine pro- 
duces an electric current by means of the electro-motive forces 
so generated. Sometimes the field is rotated ; sometimes 
both armature and field rotate. 

The armatures of dynamo-electric machines are of a great 
variety of forms. They may for convenience be arranged under 
the following heads, viz.: 

Cylindrical or drum armatures, disc armatures, pole or 
radial armatures, ring armatures, and spherical armatures. 
For further particulars see above terms. Armatures are 
also divided into classes according to the character of the 
magnetic field through which they move— into uni-polar, b>.- 



WORDS, TERMS AND PHRASES. 41 

polar, and multi-polar armatures. (See Dynamo-Electric Ma- 
chines.) 

The term armature as applied to a dynamo-electric machine 
was derived from the fact that the iron core acts to magnet- 
ically connect the two poles of the field magnets as an ordi- 
nary armature does the poles of a magnet. 

Armatures of Holt z Machine.— A badly chosen term 
for the pieces of paper on the stationary plate of the Holtz and 
other similar machines. 

Armature, Polarized An armature that pos- 
sesses a polarity independent of that imparted by the mag- 
net pole near which it is placed. 

In permanent magnets the ai matures are made of soft iron, 
and therefore, by induction, become of a polarity opposite to 
that of the magnet poles that lie nearest them. They have, 
therefore, only a motion of attraction towards such poles. 
(See Induction, Magnetic.) 

In electro-magnets the armatures may either be made of 
soft iron, in which case they are attracted only on the passage 
of the current ; or they may be formed of permanent steel 
magnets, or may be electro-magnets themselves, in which 
case the passage of the current through the coils of the elec- 
tro-magnet or electro-magnets may cause either attraction 
or repulsion according as the adjacent poles are of opposite 
polarity or are of the same polarity. 

Armature Coils, Dynamo The coils of wire 

or conductors on the armature of a dynamo-electric machine. 
(See Dynamo-Electric Machine, Armature Coils.) 

Armature Core, Dynamo The core of iron 

around or on which the armature coils are wound or disposed. 
(See Dynamo-Electric Machine, Armature Cores.) 

Armor of Cable. — The protecting sheathing or metallic 
covering" on the outside of a submarine or other electric cable. 



42 



A DICTIONARY OF ELECTRICAL 




Arms of Bridge or of Elec- 
tric Balance.— The electric re- 
sistances in an apparatus for the 
p measurement of resistance, known 
as Wheatstone's Balance or Bridge. 
An unknown resistance, such for 
example, as that at D, Fig. 25, is 
measured by so proportioning- the 
known resistances A, C, and B, 
that no current Hows through the 
Fig. 25. galvanometer G, across the circuit 

or bridge M G N. (See Balance, Wheatstone's Electric.) 

A nil* or Brackets, Telegraphic Arms or 

brackets placed on telegraph poles for the support of the in- 
sulators. (See Brackets or Arms, Telegraphic.) 

Arrester, Lightning A device for protecting 

instruments on any line from disturbance by lightning. (See 
Lightning Arrester.) 
Artificial Carbons. — (See Carbons, Artificial.) 
Artificial Illumination.— (See Illumination, Artificial.) 
Artificial Magnets. — Any magnet not formed naturally. 
All magnets other than magnetic iron ore, or lodestone, or 
meteoric iron. (See Magnets, Artificial.) 

Articulate Speech. — The successive tones of the human 
voice that are necessary to produce intelligible words. 

The phrase articulate speech refers to the joining or arti- 
culation of the successive sounds involved in speech. The 
receiving diaphragm of a telephone is caused to reproduce 
the articulate speech uttered near the transmitting diaphragm. 
Asphyxia. — Suspended respiration, resulting eventually in 
death, from the non-aeration of the blood. 

In cases of insensibility by an electric shock a species of 
asphyxia is sometimes brought about. This is due, probably, 
to the failure of the nerves and muscles that carry on respira- 



WORDS, TERMS AND PHRASES. 



43 




tion. The exact manner in which death by electrical shock 
results is not known. (See Death, Electrical.) 
Astatic Circuits.— (See Circuits, Astatic.) 

Astatic Needle. — A magnetic needle consisting of two 
magnets rigidly connected together and placed parallel and 
directly over each other, with opposite poles opposed. 

An astatic needle is shown 
in Fig. 26. The two mag- 
nets N S, and S' N', are di- 
rectly opposed in their po- 
larities, and are rigidly con- 
nected together by means of 
the axis a a. So disposed, 
the two magnets act as a 
very weak single needle 
when placed in a magnetic [Jot 

field. Fig. 26. 

Were the two magnets N S, and S' N', of exactly equal 
strength, with their poles placed in exactly the same ver- 
tical plane, they would completely neutralize each other, and 
the needle would have no -directive tendency. Such a system 
would form an Astatic Pair or Couple. 

In practice it is impossible to do this, so that the needle has 
a directive tendency, which is often east and west. 

The cause of the east and west directive tendency of an 
unequally balanced astatic system will 
be understood from an inspection of Fig. 
27, a. Unless the two needles, n s, and 

s'n', are exactly opposed, they will form - w ra 1 ; <? f -«- 

a single short magnet, N N N N, S S S S, j 

the poles of which are on the sides of (» 

the needle. The system pointing with Fig. 27, a. 

its sides due N. and S. will appear to have an east and west 

direction. 

An astatic needle possesses the valuable property of requir- 
ing a smaller force to deflect it than a sing'le needle with 




44 



A DICTIONARY OF ELECTRICAL 



more powerful poles. Its magnetism is not as easily lost or 
reversed as that of a weaker magnet. 

The principal use of the astatic needle is in the astatic gal- 
vanometer, in which the needle is deflected by the passage of 
an electric current through a conductor placed near the 
needle. Therefore it is evident that one of the needles must 
be outside and the other inside the coil. In the most sensi- 
tive form of galvanometer there is also a coil surrounding 
the upper needle, the two coils being oppositely connected, so 
that the deflection on both needles is in the same direction, 
and the deflecting power is equal to the sum of the two coils, 
while the directive power of the needles is the difference 
of their magnetic intensities. 
In the astatic system, shown in Fig. 27, the current, en- 
tering at -f- and flowing out at — , 
flows above one needle, S N, and below 
the other, S' N', and therefore de- 
flects both in the same direction, 
since their poles point in opposite di- 
rections. 

In some galvanometers a varying 
degree of sensitiveness is obtained by 
jjiijl means of a magnet, called a com- 
§§HP==- pensating magnet placed on an axis 
Fig. 27. above the magnetic needle. As the 

compensating magnet is moved towards or away from the 
needle the effect of the earth's field is varied, and with it the 
sensitiveness of the galvanometer. Such a magnet may form 
with the needle an astatic system. (See Compensating Magnet.) 
(See Galvanometer, Astatic. Galvanometer, Mirror. Mul- 
tiplier, Schiveigger's). 
Astatic Galvanometer.— (See Galvanometer, Astatic.) 
A§tatie System.— A term applied to an astatic combina- 
tion of magnets. 

Asymptote.— A curved line that continually approaches a 
straight line but never meets it. 







S- 


— nJ 


"^ < 


» = 3= j =:= '-i 




WORDS, TERMS AND PHRASES. 45 

In Fig. 28, the asymptote C D continually 
approaches the line y z, but never meets it. 

This mathematical conception is like a 
value which, although constantly reduced 
to one-half of its former value, is never- - 
theless never reduced to zero or no value. Fig. 28. 

Atmosphere, The The ocean of air that sur- 
rounds the earth. 

The atmosphere is composed, by weight, of oxygen 23 parts, 
nitrogen 77 parts, carbonic acid gas from 4 to 6 parts in 10,000 
(or about a cubic inch of carbonic acid to a cubic foot of air), 
together with varying proportions of the vapor of water. 

Besides these constant ingredients there are in most locali- 
ties a number of other substances present as impurities. 

Atmosphere, An A pressure of a gas or fluid 

equal to about 15 pounds to the square inch. 

At the level of the sea the atmosphere exerts a pressure of 
about 15 pounds avoirdupois on every square inch of the earth's 
surface. This has therefore been taken as a unit of fluid 
pressure. 

For more accurate measurements pounds to the square inch 
are employed. 

Atmospheric pressures are measured by instruments called 
Manometers. (See Manometer.) 

Atmosphere, Residual The trace of air or 

other gas remaining in a space which has been exhausted of 
its gaseous contents by a pump or other means. 

It is next to impossible to remove all traces of air from a 
vessel by any known form of pump or other appliance. (See 
Vacuum, Absolute.) 

Atmospheric Electricity. — The free electricity almost 
always present in the atmosphere. 

The free electricity of the atmosphere is generally positive, 
but often changes to negative on the approach of fogs and 



46 A DICTIONARY OF ELECTRICAL 

clouds. It exists in greater quantity in the higher regions of 
the air than near the earth's surface. It is stronger when the 
air is still than when the wind is blowing. It is subject to 
yearly and daily changes in its intensity, being stronger in 
winter than in summer, and at the middle of the day than 
either at the beginning or the close. 

Atmospheric Electricity, Origin of The ex- 
act cause of the free electricity of the atmosphere is un- 
known. 

Feltier ascribes the cause of the free electricity of the at- 
mosphere to a negatively excited earth, which charges the 
atmosphere by induction. (See Induction, Electrostatic.) 
It has been ascribed to the evaporation of water ; to the con- 
densation of vapor ; to the friction of the wind ; to the motion 
of terrestrial objects through the earth's magnetic field ; to in- 
duction from the sun and other heavenly bodies ; to differ- 
ences of temperature ; to combustion, and to gradual oxida- 
tion of plant and animal life. It is possible that all these 
causes may have some effect in producing the free electricity 
of the atmosphere. 

Whatever the cause of the free electricity of the atmosphere, 
there can be but little doubt that it is to the condensation of 
aqueous vapor that the high difference of potential of the 
lightning flash is due. (See Difference of Potential.) As the 
clouds move through the air they collect the free electricity on 
the surfaces of the minute drops of water of which clouds are 
composed, and when many thousands of these subsequently 
collect in larger drops the difference of potential is enor- 
mously increased in consequence of the equally enormous de- 
crease in the surface of the single drop over the sum of the 
surfaces of the coalescing drops. 

Atom. — The smallest quantity of elementary or simple 
matter that can exist. 

The ultimate particle of matter. 

Atom means that which cannot be cut. It is generally 



WORDS, TERMS AND PHRASES. 4? 

agreed, that material atoms are absolutely unalterable in size, 
shape, weight and density ; that they can neither be cut, 
scratched, flattened, nor distorted; and that they are unaffected 
in size, densit}", or shape, by heat or cold, or by any known 
physical force. 

Although almost inconceivably small, atoms nevertheless 
possess a definite size and mass. According to Sir Wm. 
Thomson, the smallest visible organic particle, 1-4000 of a 
millimetre in diameter, will contain about 30,000,000 atoms. 

Such a number of grammes of 



any elementary substance as is numerically equal to the 
atomic weight of the substance. 

The gramme-atom of a substance represents the number 
of calories, required to raise the temperature of one gramme 
of that substance through 1° C. (See Heat, Atomic. Calo- 
rie.) 

Atomic Attraction.— The attraction that causes the 
atoms to combine. (See Affinity. Chemical ) 

Atomic Energy.— (See Energy, Atomic) 

Atomic Heat.— (See Heat, Atomic.) 

Atomicity. — The combining capacity of the atoms. 

The relative equivalence of the atoms or their atomic ca- 
pacity. 

The elementary atoms do not always combine atom for 
atom. Some single atoms of certain elements will combine 
with two, three, four, or even more atoms of another ele- 
ment. 

The value of the atomic capacity of an atom is called its 
quantivalence or valency. 

Elements whose atomic capacity is — 

One, are called Monads, or Univalent. 
Two, " " Dyads, t; Bivalent. 
Three, " " Triads, •' Tnvalent. 
Four, " " Tetrads, " Quadrivalent. 



48 A DICTIONARY OF ELECTRICAL 

Five, are called Pentads, or Quinquivalent. 
Six, " " Hexads, " Sexivalent. 
Seven, " " Heptacls, " Septivalent. 

Atomic Weight.— The relative weights of the atoms of 
elementary substances. 

Since the atoms are assumed to be indivisible, they must 
unite or combine as wholes and not as parts. Although we 
cannot determine exactly the actual weights of the different 
elementary atoms, yet we can determine their relative 
weights by ascertaining the smallest proportions in which 
any two atoms that combine atom for atom will unite with 
each other. Such numbers will represent the relative weights 
of the atoms. 

\ tomization. — The act of obtaining liquids in a spray of 
finely divided particles. 

Atomizer. — An apparatus for readily obtaining a finely 
divided jet or spray of liquid 

A jet of steam, or a blast of a»r, is driven across the open end 
of a tube that dips below the surface of the liquid to be atom- 
ized. The partial vacuum so formed draws up the liquid, 
which is then blown by the current into a tine spray. 

Attracted I>isc Electrometer.— (See Electrometer, 
Attracted Disc.) 

Attraction. — Literally the act of drawing together. 

In science, a name for a series of unknown causes that 
effect, o." are assumed to effect, the drawing together of 
atoms, molecules or masses. 

The phenomena of attraction and repulsion underlie nearly 
all natural phenomena. While their effects are well known, 
it is doubtful if anything is definitely known of their true 
causes. 

Attraction, Atomic. (See Affinity, Chemical.) 

Attraction, Electro-Dynamic —The mutual 



WORDS, TERMS AND PHRASES. 



49 



attraction of electric currents, or of conductors through which 
electric currents are passing. (See Electro- Dynamics.) 

Attraction, Electro -Magnetic The mutual 

attraction of the unlike poles of electro-magnets. (See Elec- 
tro-Magnet.) 

Attraction, Electrostatic The mutual attrac- 
tion exerted between unlike electric charges, or bodies pos- 
sessing unlike electric charges. 





Fig. 29. Fig. 29a. 

For example, the pith ball supported on an insulated string 
is attracted, as shown at A, Fig. 29, hy a bit of sulphur which 
has been briskly rubbed by a piece of silk. As soon, however, 
as it touches the sulphur and receives a charge, it is repelled, 
as shown at B, Fig. 29a. 

These attractions and repulsions are due to the effects of 
electrostatic induction. (See Induction, Electrostatic.) 



Attraction, Ulasriietic- 



-The mutual attraction 



exerted between unlike magnet poles. 

Magnetic attractions and repulsions are best shown by 
means of the magnetic needle N S, shown in Fig. 30. The 
N. pole of an approached magnet attracts the S. pole of 
the needle but repels the X. pole. 



50 



A DICTIONARY OF ELECTRICAL 



The laws of magnetic attraction 
stated as follows, viz. : 

N 





and repulsion may be 



(1) Magnet poles 
of the same polarity 
repel each other. 

(2) Magnet poles 
cf unlike names at- 
tract each other. 

A small bar mag- 



laid on the top of a 
light vessel floating on the surface of a 
liquid, may be readily employed to illus- 
trate the laws of magnetic attraction and 
repulsion. 

Attraction, Mass or Molar 

Gravitation. — The mutual attraction exerted between 
masses of matter. (See Gravitation.) 

Attraction, Molecular 

=, The mutual attraction exerted between 
molecules. 
|pii=~ The attraction of like molecules, or 

Fig. 31. those of the same kind of matter, is 

called Cohesion ; that of unlike molecules, Adhesion. 

The strength of iron or steel is due to the cohesion of its 
molecules. Paint adheres to wood, or ink to paper, by the 
attraction between unlike molecules. 

Audiphone. — A thin plate of hard rubber placed in the 
human mouth in contact with the teeth, and maintained at a 
certain tension by strings attached to one of its edges, for the 
purpose of aiding the hearing. 

The plate is so held that the sound-waves from a speaker's 
voice impinge directly against its flat surface. It operates by 
means of some of the waves being transmitted to the ear 
directly through the bones of the head, 




WORDS, TERMS AND PHRASES. 51 

Aurora Korea I is. — Literally, the Northern Light. Lu- 
minous sheets, columns, arches, or pillars of a pale flashing 
light, generally of a red color, seen in the northern heavens. 

The auroral light assumes a great variety of appearances, to 
which the terms auroral arch, bands, coronce, curtains and 
streamers are applied. 

The exact cause of the aurora is not as yet known. It 
would appear, however, beyond any reasonable doubt, that 
the auroral flashes are due to the passage of electrical cur- 
rents or discharges through the upper, and therefore rarer, 
regions of the atmosphere. The intermittent flashes of 
light are probably due to the discharges being influenced by 
the earth's magnetism. 

Auroras are frequently accompanied by magnetic storms. 
(See Magnetic Storms.) 

The occurrence of auroras is often simultaneous with 
that of an unusual number of sun spots. Auroras are there- 
fore probably connected with outbursts of the solar en- 
ergy. (See Sun Spots.) 

The auroral light examined by the spectroscope gives a 
spectrum characteristic of luminous gaseous matter, i. e., 
contains a few bright lines ; but, according to S. P. Thomp- 
son, this spectrum is produced by matter that is not refer- 
able with certainty to that of any known substance on the 
earth. 

Whatever may be the exact cause of auroras, their ap- 
pearance is almost exactly reproduced by the passage of elec- 
tric discharges through vacuous spaces. (See Geissler Tubes.) 

Aurora Australis. — The Southern Light. A name given 
to an appearance in the southern heavens similar to that of 
the Aurora Borealis, 

Austral Pole. — A name sometimes employed in France 
for the north-seeking pole of a magnet. 

That pole of a magnet which points to the earth's geo- 
graphical north. 



52 



A DICTIONARY OF ELECTRICAL 



It will be observed that the French regard the magnetism 
of the earth's Northern Hemisphere as north, and so name the 
north-seeking pole of the needle, the austral or south pole. 

battery The south-seeking pole 

of the magnet is some- 
times called the boreal or 
north pole. (See Boreal 
Pole.) 

Automatic Burner. 

— (See Burner, Auto- 
matic, Electric.) 

Automatic Contact 
Breaker, or Auto- 
matic lake-and- 
Break.— A device for 
causing an electric cur- 
rent to rapidly make and 
break its own circuit. 

The spring c, Fig. 32, 
carries an armature of 
soft iron, B, and is placed in a circuit in such a manner that 
the circuit is closed when platinum contacts placed on the 
ends of D and B touch each other. In this case the arm- 
ature B is attracted to the core A, of the electro-magnet, 
thus breaking the circuit and causing the magnet to lose its 
magnetism. The elasticity of the spring C, causes it to fly 
back and again close the contacts, thus again energizing the 
electro-magnet and again attracting B, and breaking the 
circuit. The makes and breaks usually follow each other so 
rapidly as to produce a musical note. (See Alarm, Electric.) 

Automatic Cut-Out, Electric A device by 

means of which an electric circuit is either opened or short 
circuited, whenever the current passing might injure the 
electro receptive devices, (See Short Circuit.) 




BA1TERV 



Fig, 32. 



WORDS, TERMS AND PHRASES. 53 

The safety devices for arc lights, or series circuits, differ in 
their construction and operation from those for incandescent 
lights, or multiple circuits. (See Circuits, Varieties of. 
Safety Device for Arc Light Circuits. Safety Catch. Cut- 
out, Automatic. Safety-Fuse. Safety-Strip. Fusible Plug.) 

Automatic Regulation.— Such a regulation of a dy- 
namo-electric machine as will preserve constant either the 
current or the electro-motive force generated by it. 

The automatic regulation of dynamo-electric machines may 
be accomplished in the following ways, viz. : 

(1) By a Compound Winding of the machine. 

This method is particularly applicable to constant-potential 
machines. By this winding the magnetic strength of the shunt- 
coils is constant, while that of the series-coils varies proportion- 
ally to the load on the machine. The series-coils are prefer- 
ably wound close to the poles of the machine, and the shunt- 
coils nearer the yoke of the magnets. Custom, however, varies 
in this respect, and very generally the shunt-coils are placed 
nearer the poles than the series-coils. (See Compound-Wind- 
ing, Dynamo-Electric Machines.) 

(2) By Shifting the Position of the Collecting Brushes. 

In the Thomson-Houston system the current is kept prac- 
tically constant by the following devices : The collecting 
brushes are fixed to levers moved by the regulator magnet R, 
as shown in Fig. 33, the armature of which is provided with 
an opening for the entrance of the paraboloidal pole piece A. 
A dash-pot is provided to prevent too sudden movement. 

When the current is normal, the coil of the regulator mag- 
net is short-circuited by contact points at S T which act as 
a shunt of very low resistance. These contact-points are 
operated by the solenoid coils of the Controller traversed by 
the main current. The cores of this solenoid are suspended 
by a spring. When the current becomes too strong the con- 
tact-point is opened, and the current, traversing the coil of 
the regulator magnet A attracts its armature, which shifts 



54 



A DICTIONARY OF ELECTRICAL 



the collecting brushes into a position at which a smaller cur- 
rent is taken off. A carbon shunt, r, of high resistance, is 
provided to lessen the spark at the contact-points S T, which 
occurs on opening the circuit. 





SMlflOr 



Fig. 33. 

In operation the contact-points are continually opening 
and closing, thus maintaining a practically constant current 
in the external circuit. 

(3) By the Automatic Variation of a Resistance shunting 
the field magnets of the machine, as in the Brush System. 

In Fig. 34, the variable resistance C forms a part of the 
shunt circuit around the field magnets F M. This resistance is 
formed of a pile of carbon plates. On an increase of the cur- 
rent, such, for example, as would result from turning out 
some of the lamps, the electro-magnet B, placed in the main 
circuit, attracts its armature A, and, compressing the pile of 
carbon plates C, lowers their resistance, thus diverting a pro- 
portionally larger portion of the current from the field magnet 
coils F M, and maintaining the current practically constant. 

In some machines the same thing is done by hand, but this 
is objectionable, since it requires the presence of an attendant. 



WORDS, TERMS AND PHRASES. 



55 




Fig. 3h. 



4. By the Introduction of a Variable Resistance into the 
shunt circuit of the machine, as in the Edison and other 
systems. 

This resistance may 
b e adjusted either 
automatical] y by an 
electro- mag net 
whose coils are in an 
independent shunt 
across the mams, or 
may be operated by 
hand. 

In Fig. 35, the vari- 
able resistance is 
shown at R, the lever switch being in this case operated by 
hand whenever the potential rises or falls below the proper 
value. 

The machine 
shown is thus en- 
abled to maintain a 
constant potential on 
the leads to which 
the lamps, L L L, 
etc., are connected in 
multiple-arc. 

5. Dynamometric 
Governing, in which 
a series dynamo is 
made to yield a con- 
stant current by gov- 
erning the steam engine that drives it, by means of a dynamo- 
metric governor that maintains a constant torque or turning 
moment, instead of the usual contrifugal governor which 
maintains a constant speed. 

6. Electric Governing of the Driving Engine, in which the 



1 


r 

< 


< 
' < 
i . 

> i 

> c 


, — ■' 

1 
.» 


U 




Fig. 35. 



56 



A DICTIONARY OF ELECTRICAL 



governor is regulated by the current itself instead of by the 
speed of rotation as usual. 

(See Addendum Automatic Regulation.) 

Automatic Telegraphy.— (See Telegraphy, Automatic.) 

Automatic Telephone Switch.— (See Switch, Tele- 
phone, Automatic.) 

Average Electro-UIotive Force.— The mean value of 
a number of separate electro-motive forces of different values. 

When a wire in the armature of a dynamo-electric machine 
cuts the lines of magnetic force in the field of the machine, 
the electro-motive forces produced depend on the number of 
lines of force cut per second. This will vary for different 
positions of the coil. The mean of the varying E. M. F.'s 
is the average E. M. F. 

Axe§ of Co-Ordinates.— (See Co-Ordinates, Axes of.) 
Axis of Abscissas. — (See Abscissas, Axis of.) 
Axis of Ordinate*.— (See Abscissas, Axis of.) 




Axis, 



of a 



Magnetic — 
Straight Needle. — A straight line 
drawn through the magnet, joining its 
poles. 

The magnetic axis of a straight needle 
may be regarded as a straight line 
passing through the poles of the needle 
and its point of support. 

The magnetic axis may not corre- 
spond with the geometric axis of the 
needle. This leads to an error in read- 
ing the true direction in which the 
needle is pointing, which must be cor- 
rected. Thus, the needle N S, Fig. 36, 
points to 31° on the scale. In reality, if the magnetic axis of 
the needle lies in the line N' S', the true deflection of the 
needle is only 28°. 



WORDS, TERMS AND PHRASES. 57 

Azimuth.— In astronomy, the angular distance between 
an azimuth circle and the meridian. 

The azimuth of a heavenly body in the Northern Hemisphere 
is measured on the arc of the horizon intercepted between the 
north point of the horizon, and the point where the great circle 
that passes through the heavenly body cuts the horizon. 

Azimuth Circle. — The arc of a great circle passing 
through the point of the heavens directly overhead, called 
the Zenith, and the point directly beneath, called the Nadir. 

Azimuth Compass. — A compass employed by navigators 
for measuring the horizontal distance of the sun or a star from 
the magnetic meridian. (See Compass, Azimuth.) 

Azimuth, Magnetic The arc intercepted on the 

horizon between the magnetic meridian and a great circle 
passing through the observed body. 

B. A. Ohm. — The British Association Unit of Resistance, 
adopted prior to 1884. 

The value of the Unit of Electric Resistance, or the ohm, 
was determined by a Committee of the British Association 
as being equal to the resistance of a column of mercury 
at 0° C, one square millimetre in area of cross-section and 
104.9 centimetres in length. This length was taken as com- 
ing nearest the value of the true ohm deduced experimentally 
from certain theoretical considerations. Subsequent re-deter- 
minations showed the value so obtained to be erroneous. 
The value of the ohm is now taken internationally, as adopted 
by the International Electric Congress in 1884, as the resistance 
of a column of mercury 106 centimetres in length, and one 
square millimetre in area of cross-section. This last value is 
called the legal ohm, to distinguish it from the B. A. ohm 
which, as above stated, is equal to a mercury column 104.9 
centimetres in length. Usage now sanctions the use of the 
word ohm to mean the legal ohm. 

This value of the legal ohm is provisional until the exact 
length of the mercury column can be finally determined. 



58 A DICTIONARY OF ELECTRICAL 

The following are the relative values of these units, viz. : 

1 Legal Ohm = 1.0112 B. A. Ohm. 

" = 1.0600 Siemens Unit. 

1 B. A. Ohm = .9889 Legal Ohm. 

1 B. A. Ohm = 1.0483 Siemens Unit. 

1 Siemens Unit = .9540 B. A. Ohm. 

" = .9434 Legal Ohm. 

Back Electro-Molive Force. — A term sometimes used 
for Counter Electro-Motive Force. The term counter electro- 
motive force is the preferable term. (See Counter Electro- 
Motive Force.) 

Back or Return Stroke of Lightning.— An elec- 
tric shock, caused by an induced charge, produced after the 
discharge of a lightning flash. 

The shock is not caused by the lightning flash itself, but by 
a charge which is induced in neighboring conductors by the 
discharge. A similar effect may be noticed by standing near 
the conductor of a powerful electric machine, when shocks 
are felt at every discharge. 

The effects of the return shock are sometimes quite severe. 
They are often experienced by sensitive people on the occur- 
rence of a lightning discharge at a considerable distance. 

In some instances the return stroke has been sufficiently 
intense to cause death. In general, however, the effects are 
much less severe than those of the direct lightning discharge. 

Balance, Arms of (See Arms of Bridge or Elec- 
tric Balance.) 

Balance, Bi-filar Suspension An instrument 

similar in its construction to Coulomb's torsion balance, but in 
which the needle is hung by two fibres instead of a single one. 

Any deflection of the needle shortens the vertical distance 
between the points of support and the needle, and so tends to 
lift the needle. The motions are therefore balanced against 
the force of gravity instead of against the torsion of the 
fibre. 



WORDS, TERMS AND PHRASES. 



m 



Fig. 37. 
between the 



A bi-filar suspension is shown in Fig-. 37. The two threads, 
a b and a' b', are connected to the needle M N, so as to 
permit it to hang in a true horizontal c 

position. Any twisting- around the im- «',<?' 

aginary axis c c', causes the lines of sus- 
pension, a b and a b' , to tend to cross 
one another and so shorten the axis 
c c'. 

Harris, who was the first to employ 
the bi-filar suspension, showed that the 
reactive force imparted to the suspension- 
threads by turning the needle was : 

(1) Directly proportional to the distance 
threads. 

(2) Inversely as their lengths. 

(3) Directly proportional to the weight of the suspended body. 

(4) As the angle of twist or torsion of the threads on each 
other. 

Balance, Cou- 
lomb's Torsion 

— An apparatus to meas- 
ure the force of electric 
or magnetic repulsion be- 
t w e e n two similarly 
charged bodies, or be- 
tween two similar mag- 
net poles, by opposing- to 
such force the torsion of 
a thin wire. 

The two forces balance 
each other ; hence the 
origin of the term. 

Fig. 38 represents a 
Coulomb torsion balance 

Won ^R 

adapted to the measure- 
ment of the force of electrostatic repulsion. A delicate needle 




A DICTIONARY OF ELECTRICAL 



of shellac, having a small gilded pith ball at one of its ends, 
is suspended by a fine metallic wire. A proof-plane B is 
touched to the electrified surface whose charge is to be 
measured, and is then placed as shown in the figure. (See 
Proof-Plane.) There is a momentary attraction of the needle, 
and then a repulsion, which causes the needle to be moved 
a certain distance from the ball on the proof-plane. This 
distance is measured in degrees on a graduated circle a a 
marked on the instrument. The force of the repulsion 
is calculated by determining the amount of torsion required to 
move the needle a certain distance towards the ball of the 
electrified proof-plane. 

This torsion is obtained by the movement of the torsion 
head D, the amount of which motion is measured on a gradu- 
ated circle at D. The measurement is based on the fact that the 
torsional force of a wire is proportional to the angle of torsion. 

Balance, Hughes' Induction An apparatus 

for the detection of the presence of a metallic substance by 
the aid of induced electric currents. 




H"flf-^y^ 



Fig. 39. 



Two small primary coils of wire, Pj and P 2 , Fig. 39, are 
placed in the circuit of the battery B, and microphone M, 
(See Microphone.) Two small secondary coils, Sj and S 2 , are 
placed near them in the circuit of a telephone, T, When the 
induction between P x and S r is exactly equal to that between 



WORDS, TERMS AND PHRASES. 



61 



P 2 and S 2 no sound is heard in the telephone, since the cur- 
rents induced in S x and S 2 exactly neutralize or balance each 
others effects. 
If a single coin or mass of metal be introduced between 



and a sound will be heard, since some of the induction is now 
expended in producing- electric currents in the interposed 
metal, and a sound will therefore be heard in the telephone. 
But if precisely similar metals are placed in similar positions, 
between S x and P 1? and S 2 and P 2 , no sound is heard in the 
telephone, since the inductive effects due to the two metals 
are the same. 

The slightest difference, however, either in composition, 
size, or position, destroys the balance, and causes a sound to 
be heard in the telephone. 

A spurious coin is thus readily detected when compared 
with a genuine coin. 

A somewhat similar instrument has been employed to 
detect and locate a bullet or other foreign metallic substance 
in the human body. 

Balance, Thermic (See Bolometer, or Thermic 

Balance.) 

Balance, Wheatstone's 

Electric A device for 

measuring the value of electric re- 
sistances. Q 

A, B, C and D, Fig. 40, are four 
electric resistances, any one of 
which can be measured in ohms, 
provided the absolute value of one 
of the others, and the relative values 
of any two of the remaining three 
are known in ohms. 

A voltaic battery, Zn C, is connected at Q and P, so as 
to branch at P and again unite at Q, after passing- through 
the conductor D C and B A. 




62 A DICTIONARY OF ELECTRICAL 

A sensitive galvanometer, G, is connected at M N, as 
shown. 

The passage of a current through any resistance is attended 
by a fall of potential that is proportional to the resistance. 
(See Potential, Electric.) If then the resistances A, C and B, 
are so proportioned to the value of the unknown resistance 
D, that no current passes through the galvanometer G, the 
two points, M and N, in the two circuits, QMP and QNP, 
are at the same potential. That is to say, the fall of poten- 
tial along Q M P and Q N P, at the points M and N, is 
equal. Since the fall of potential is proportional to the resist- 
ance it follows that 

A : B : : C : D, 
or A X D = B X C, 

°" D =(l) c - 

If then we know the values of A, B and C, the value of D 
can be readily calculated. 
B 

By making the value — some simple ratio, the value of D is 
A 
easily obtained in terms of C. 

The resistances A, B and C, may consist of coils of wire 
whose resistance is known. To avoid their magnetism affect- 
ing the needle during the passage of the current through them, 
they should be made of wire bent into two parallel wires 
and wrapped in coils called resistance coils, or a resistance-box 
may be used. (See Coils, Resistance. Box, Resistance.) 

There are two general forms of Wheatstone's Balance, viz. : 
the box form, and the sliding form. 

Balance, Wheatstone's Electric , Box or 

Commercial Form of Wheatstone's Bridge. — A 

commercial form of bridge or balance in which all three known 
arms or branches of the bridge consist of standardized resist- 



WORDS, TERMS AND PHRASES. 



63 



ance coils, whose values 
Resistance.) 




Fig. hi. 



are given in ohms. (See Coils, 



The box form of 
bridge is shown in 
perspective in Fig. 
41, and in plan in 
Fig. 42. The bridge 
arms, correspond- 
ing to the resist- 
ances A and B, of 
Fig. 40, consist of 
resistance coils of 
10, 100, and 1,000 



ohms each, insert- 
ed in the anus qz, 
and q x, of Fig. 
42. (See Balance. 
Whea ts tone's 
Electric.) These 
are called the pro- 
portional coils. 
The arm corre- 
sponding to resist- 







T 


looo ioo io q io ioo 1000 


3) 








6 


oWotfoHo<5>oHo tf O w oi 


2 


6 

D 


s 

i a a 6 io io 20 so 

o^~o ft o ft o ft o ft~o ft o ft o ft 








^ww aow looo low mo m ioo ioo , 

/ ((>)o^ o j(o{(oj)o}|o)(cj|o \( 

r 


§ 




induction, among- 



Fig. U2. 
ance C, of Fig. 40, is composed 
of separate resistances of 1, 2, 
2, 5, 10, 10, 20, 50, 100, 100, 200 
500, 1,000, 1,000, 2,000, and 
5,000 ohms. In some forms 
of box bridges, additional 
decimal resistances are added. 
The resistance coils are 
wound, as shown in Fig. 43, 
after the wire has been bent 
on itself in the middle, in 
order to avoid the effects of 
which are a disturbing action on a gaivano- 



u 



A DICTIONARY OF ELECTRICAL 



meter used near them, and the introduction of a spurious 
resistance in the coils themselves. (See Spurious Resistance.) 
To avoid the effects of changes of resistance occasioned by 
changes of temperature, the coils are made of German silver, 
or preferably of alloys called Platinoid, or Platinum silver. 
(See Platinoid. Platinum Silver.) Even when these alloys are 
used, care should be taken not to allow the currents used to 
pass through the resistance coils but for a few moments. 

The coils, C C, are connected with one another in series by 
connecting their ends to the short, thick pieces of brass, E E E, 
Fig. 43. On the insertion of the plug keys, at S S, the coils are 
cut out by short-circuiting. Care should be taken to see that 
the plug keys are firmly inserted and free from grease or dirt, 
otherwise the coil will not be completely cut out. 

The following are the connec- 
tions, viz. : The galvanometer is 
inserted between q and r, Fig. 
44; the unknown resistance be- 
tween z and r ; the battery is 
connected to x and z. A con- 
venient proportion being taken 
for the value of the proportional 
coils, resistances are inserted in 
C, until no deflection is shown by 
the galvanometer G. The simi- 
larity between these connections and those shown in Fig. 42. 
will be seen from an inspection of Fig. 44. (See Balance, 
Wheatstone's Electric.) The arms, A and B, correspond to 
q x and q z, of Fig. 42 ; C, to the arm x r, Fig. 42 ; and D, to 
the unknown resistance. We then have as before 

A : B : : C : D., or AXD = BXC, .-. D= ( — ) C. 

The advantage of the simplicity of the ratios, A and B, or 
10, 100, and 1,000 ? of the Bridge Box, will therefore be mani- 




WORDS, TERMS AND PHRASES. 65 

fest. The battery terminals may also be connected to q and r, 
and the galvanometer terminals to x and z, without disturb- 
ing' the proportions. 



Fig. U5. 
Balance, Wheatstone's, Slide Form of- 



66 A DICTIONARY OF ELECTRICAL 

balance in which the proportionate arms of the bridge are 
formed of a single thin wire, of uniform diameter, generally of 
German silver, of comparatively high resistance. 

A Spring Key slides over the wire ; one terminal of the key 
is connected with the galvanometer and the other with the 



gfllo n>t«i> tnira) ~ "nU B 



Eld, 



( 00 I 860 I 



Fig. IS. 

wire when the spring key is depressed. As the wire is of 
uniform diameter, the resistances of the arms, A and B, Fig. 
46, will then be directly proportional to the lengths. A scale 
placed near the wire serves to measure these lengths. A 
thick metal strip connected to the slide wire has four gaps at 
P, Q, R and S. 

When in ordinary use, the gaps at P and S are either con- 
nected by stout strips of conducting material or by known 
resistances, in which case they act simply as un graduated 
extensions of the slide wire, and, like lengthening the slide 
wire, increase the sensibility of the instrument. 

The unknown resistance is then inserted in the gap at Q, 
and a known resistance, generally the resistance box, in that 
at E. The galvanometer has one of its terminals connected 
to the metal strip between Q and R, and its other terminal to 
the sliding key. The battery terminals are connected to the 
metal strips between P and Q, and R and S, respectively. 

These connections are more clearly seen in the form of 
bridge shown in Fig. 45. The slide wire w w, consists of three 
separate wires each a metre in length, so arranged that only 
one wire, or two in series, or all three in series, can be used. 
Matters being now arranged as shown, the sliding key is 
moved until no current passes through the galvanometer. 



WORDS, TERMS AND PHRASES. 



i;t 



The sliding bridge is not entirely satisfactory, since the 
uncertainty of the spring-contact causes a lack of correspond- 
ence between the point of contact and the point of the scale 
on which the index rests. 

The loss of uniformity of the wire, due to constant use, 
causes a lack of correspondence between the resistance of the 
wire and ils length. With care, however, very accurate re- 
sults can be obtained. 

Ballistic Curve. — The curve actually described by a pro- 
jectile thrown in any other than a vertical direction through 
the air. 

Theoretically, the path of a pro- 
jectile in a vacuum is a parabola 
—that is, the path A E B, Fig. 47. 
Actually, the effects of fluid resist- 
ances cause it to take the path A 
C D, called a ballistic curve. The 
ballistic curve has a smaller verti- 
cal height than the parabola. The 
projectile also has a smaller vertical range. Instead of reach- 
ing the point B, it continually approaches the perpendicular 
EF. 

Ballistic Galvanometer.— A form of galvanometer 
suitable for measuring* momentary currents, such as those 
produced by the discharge of a condenser, winch rise rapidly 
from zero to a maximum, and then as rapidly fall to zero. 
(See Galvanometer, Ballistic.) 

Barart— A unit of pressure recently proposed by the Brit- 
ish Association. 

One barad equals one dyne per square centimetre. 

Barometer. — An apparatus for measuring the pressure 
of the atmosphere. 

Barometric Column. — A column, usually of mercury, 
approximately thirty inches in vertical height, sustained in 
a barometer or other tube by the pressure of the atmosphere. 




Fig. >,. 



OS 



A DICTIONARY OF ELECTRICAL 



The space above the barometric column contains a vacuum 
known as the Torricellian vacuum. 

Bars, Krizlk'* Gores of various shapes, provided 

for solenoids, in which the distribution of the metal in the bar 
is so proportioned as to obtain as nearly as possible a uniform 
attraction or pull while in different positions in the solenoid. 

Various Krizik's 
bars are shown in 
Fig. 48. As will be 
observed, in a 1 I 
cases the mass of 
metal is greater 
towards the middle 
of the bar or core 
than near the ends. 
When a core of 
uniform diameter is 
drawn into a sole- 




Fiq. IS. 



noid, the attraction or pull is not uniform in strength for dif- 
ferent positions of 1 ho bar. When the bar is just entering the 
solenoid, the pull is the strongest; as soon as the end passes 
the middle of the core the attraction grows less, until, when 
the centres of the bar and core coincide, the motion ceases, 
since both ends of the solenoid attract equally in opposite 
directions. By proportioning the bars, asshown in the figure, 
a fairly uniform pull for a considerable length may be ob- 
tained. 

Batli, Electro-Therapeutic A bath furnished 

with suitable electrodes and used in the application of elec- 
tricity to curative purposes. Such baths should be used only 
under the advice of an intelligent physician. 

Bath, Electro-Plating — Tanks containing me- 
tallic solutions in which articles are placed that are to be 
electro-plated. (See Electro-Plating :) 

Bathometer— An instrument invented by Siemens for 



WORDS, TERMS AND PHRASES. 69 

obtaining deep-sea soundings without the use of a sounding 
'ine. 

The bathometer depends for its operation on the decreased 
attraction of the earth for a suspended weight, that takes place 
in parts of the ocean differing in depth. As the vessel passes 
over deep portions of the ocean, the solid land of the bottom, 
being further from the ship, exerts a smaller attraction than 
it would in shallow parts, where it is nearer ; for, although in 
the deep pails of the ocean the water lies between the ship 
and the bottom, the smaller density of the water as compared 
with the land causes it to exert a smaller attraction than in 
the shallower parts, where the bottom is nearer the ship. The 
varying attraction is caused to act on a mercury column, the 
reading of which is effected by means of an electric contact. 

Batlis, Copper, Gold, Silver, INiekel, etc., 

Tanks containing solutions of metals suitable for electric 
deposition by the process of electro-plating. (See Electro- 
Plating.) 

Batteries, Varieties of Voltaic (See Cell, 

Vallate. Varieties of.) 

Battery, Dynamo The combination or coup- 
ling together of several separate dynamo-electric machines so 
as to act as a single electric source. 

The dynamos may be connected to the leads either in series, 
in multiple-arc, in multiple-series, or in series-multiple. 

Battery, Electric A general term applied to 

the combination, as a single source, of a number of separate 
electric sources. 

The separate sources may be coupled either in series, in 
multiple-are, in multiple-series, or in series-multiple. (See Cir- 
cuits, Varietiesof.) 

The term battery is sometimes incorrectly applied to a single 
voltaic couple or cell. 

Battery.* L.ey<lcu Jar The combination of a 

number of separate Leyden jars so as to act as one single jar. 



70 



A DICTIONARY OF ELECTRICAL 



A Leyden battery is shown in Fig. 49, where nine separate 
Leyden jars are connected as a single jar by joining their 
outer coatings by placing them in the box P, the bottom of 




Fig. It9. 
which is lined with tin foil. The inner coatings are con- 
nected together by the metal rods B, as shown. 

A discharging rod A' may be employed for connecting the 
opposite coatings. The handles are made of glass or any 
good insulating material. 

Battery, Lot al A voltaic battery used at either 

end of a telegraph line to operate the Morse sounder, or the 
registering or recording apparatus, at that end only. (See 
Telegraphy, Morse System of.) 

The local battery is thrown into or out of action by the 
telegraphic relay. (See Relay.) 



WORDS, TERMS AND PHRASES. 



71 



Battery, Magnetic 



-The combination, as a single 



magnet, of a number of separate mag - nets. 

A magnetic battery, or compound magnet, 
is shown in Fig. 50. It consists of straight 
bars of steel, p p p, with their similar poles 
placed near together, and inserted in masses 
of soft iron, N and S, as shown. 




Battery., Pluiigc- 



A number of 

voltaic cells connected so as to form a single 
cell or electric source, the plates of which 
are so supported on a horizontal bar as 
to be capable of being simultaneously 
placed in, or removed from, the liquid. 

The plunge battery shown in Fig. 51 con- 
sists of a number of zinc-carbon elements 
immersed in an electrolyte of dilute sul- 
phuric acid, or in electropoion liquid, con- 
tained in separate jars, J, J. 



% 



NkZ=^ 



Fig. 50. 
(See Electropoion Liquid.) 





Ill II 




Battery, Primary- 



Fig. 51. 



-The combination of a num- 



ber of primary cells so as to form a single source. 

The term primary buttery is used in order to distinguish it 
from secondary or storage battery. (See Storage Celts or Accu- 
mulators.) 



72 A DICTIONARY OF ELECTRICAL 

Battery, Secondary The combination of a 

number of secondary or storage cells so as to form a single 
electric source. (See Storage of Electricity.) 

Battery, Selenium The combination of sele- 
nium with another element to form an electric source when 
acted on by light. 

Battery, Split A voltaic battery connected in 

series, and having one of its middle plates connected with 
the ground. 

By this means the poles of a battery are maintained at 
potentials differing in opposite directions from the potential 
of the earth. 

Battery, Therino-EIectric The combination, 

as a single thermo-electric cell, of a number of separate thermo- 
electric cells or couples. (See T her mo-Electric Couple.) 

Battery, Voltaic, Closed-Circuit A voltaic 

battery which may be kept constantly on closed circuit. 

The gravity battery is a closed-circuit battery. As em- 
ployed for use on most telegraph lines, it is maintained on 
a closed circuit. When an operator wishes to use the line he 
opens his switch, thus breaking the circuit and calling his 
correspondent. Such batteries should not polarize. (See 
Polarization of Voltaic Cell.) 

Battery, Voltaic, Open-Circuit A voltaic 

battery which is normally on open-circuit, and which is used 
for comparatively small durations of time on closed circuit. 

The Leclanche-cell is an excellent open-circuited battery. 
It has a comparatively high electro-motive force, but rapidly 
polarizes. It cannot therefore be economically used for 
furnishing currents continuously for long durations of time. 
When left on open circuit, however, it depolarizes. (See Cell, 
Voltaic, Leclanche.) 

Battery, Voltaic The combination, as a single 

source, of a number of separate voltaic cells. 

Battery, Water —A battery formed of zinc and 

copper couples immersed in ordinary water. 



WORDS, TERMS AND PHRASES. 73 

Any voltaic couple can be used, the positive element of 
which is capable of being slightly acted ou by water. AVhen 
numerous couples are employed considerable difference of 
potential can be obtained. 

Water batteries are employed for charging' electrometers. 
They are not capable of g-iving* any considerable current, 
owing to their great internal resistance. 

B. A. U. — A contraction sometimes employed for the Brit- 
ish Association Unit or Ohm. 

Bell Call, Electric An electric bell used to call 

the attention of an operator to the fact that his correspondent 
wishes to communicate with him. 

Bell, Extension Call A device for prolonging 

the sound of a magneto call, and for sounding the signal at 
some distant point. 

An alarm-bell is connected with the circuit of a local bat- 
tery by the current generated by the magneto call, and con- 
tinues sounding alter the current of the magneto call has 
ceased. 

Bell, Indicating An electric bell in which, in 

order to distinguish between a number of bells in the same 
office, a number is displayed by each bell when it rings. 

Bell Magnet— (See Magnet, Bell.) 

Bell, Magneto Call Telephone Call 

A call-bell operated by currents generated by the rotation of 
an armature in a magnetic field. 

Bell*, Relay -Bells used in the early forms of 

of acoustic telegraphs as employed in England with relay 
sounders. 

The dots and dashes of the Morse alphabet were indicated 
by the sounds of a bell, a tap on one bell indicating a dot, and 
a tap on the other a dash. This system is now practically 
abandoned. 

Bias of Relay Tongue.— A term to signify the adjust- 



74 



A DICTIONARY OF ELECTRICAL 



ment of a polarized relay such that, on the cessation of the 

working current, the relay tongue shall always rest against. 

the insulated contact and not against the other contact, or 

vice versa. 
Sometimes, as in the split-battery -duplex, the bias is toward 

the uninsulated contact. (See Relay, Polarized.) 
Bi< Eirouiate Voltaic Cell.— (See Cell, Voltaic.) 
Bi-Filar Balance.— (See Balance, Bi-filar Suspension.) 
Bi-Filar Suspension.— The suspension of a needle or 

magnet by two fibres in place of a single fibre. (See Bal- 
ance, Bi-Filar Suspension.) 
Bi-Filar Winding of Coils.— A winding of a coil of 

wire such that, instead of winding it in one continuous length, 

the wire is doubled in itself and then wound. 

This method is employed in resistance coils, so as to avoid 

disturbing effects on neighboring instruments. (See Coils, 

Resistance.) 

Biliary Compound.— In chemistry, a compound formed 
by the union of two different elements. 

Water is a binary compound, being formed by the union 
of two atoms of hydrogen with one atom of oxygen. Its 
chemical composition is thus expressed in chemical symbols, 
viz., H 3 0, which indicates two atoms of hydrogen combined, 
or chemically united, with one atom of oxygen. 
V 




Fig. 52. 

Binding Posts, or Binding Screws. — Devices for 
connecting the terminals of an electric source with those of an 



WORDS, TERMS AND PHRASES. 75 

electro-receptive device, or for connecting different parts of an 
electric apparatus with one another, 

The conducting or circuit wire is either introduced in the 
opening a, Fig. 52, and clamped by the screw b ; or is placed 
in the space, d d, and kept in place by means of a thumb-screw. 
Sometimes two openings are provided at c and c', for the 
purpose of connecting two wires together. 

Biology, Electro (See Electro-Biology.) 

Black Lead. — A variety of carbon employed in various 
electrical processes. 

Black lead is also termed plumbago or graphite. (See Plum- 
bago. Graphite.) 

Blasting, Electric The electric ignition of pow- 
der or other material in a blast. (See Fuse, Electric.) 

Bleaching, Electric Bleaching processes in 

which the bleaching agents are liberated as required by 
the agency of electrolytic decomposition. 

In the process of Naudin and Bidet, the current from a dy- 
namo-elect rie machine, is passed through a solution of common 
salt between two closely approached electrodes. The chlorine 
and sodium thus liberated react on each other and form so- 
dium hyphochloride, which is drawn otF by means of a pump 
and used for bleaching. (See Electrolysis.) 

Block, Branch (See Branch Block.) 

Block System for Railways. — A system for securing 
safety from collisions of moving railroad trains by dividing 
the road into a number of blocks or sections of a given length, 
and so maintaining telegraphic communication between 
towers located at the ends of each of such blocks, as to prevent, 
by the display of suitable signals, more than one train or en- 
gine from being on the same block at the same time. 

There are two kinds of block railway systems, viz. : 

(1) The Absolute Block System. 

(2) The Permissive Block System, 



A DICTIONARY OF ELECTRICAL 



In the absolute system, which is of course the safest, one 
train only is permitted to be on any particular block at a 
given time. 

In the permissive block system more than one train is per- 
mitted, under certain circumstance and conditions, to occupy 
the same block simultaneously., each train then being notified 
of the fact that it js not alone on the block. 

The absolute block system, though expensive to construct 
and maintain, is the only one that should be permitted in law 
to exist on roads whose traffic reaches a certain amount. 

The absolute block system is employed on the London Un- 
derground Railroad, and on the Pennsylvania Railroad 
Systems. 

The system, as in use on the New York division of the 
Pennsylvania Railroad, is as follows : 




Fig. 53. 

The road between Philadelphia and Jersey City is divided 
into some seventy sections, the length of each section being 
dependent on the amount of daily traffic • thus, between 
Jersey City and Newark, where the traffic is great, there are 



WORDS, TERMS AND PHRASES. 7? 

some fifteen sections, although the distance is only 7.9 
miles. 

In each block-tower there are connections with three separ- 
ate and distinct telegraph lines or circuits, viz. : 

(1) A line or wire called the train wire, connecting the 
block-tower with the General Dispatcher's office at Jersey 
City. This line is used for sending train orders only. 

(2) A line or wire called the block irire, connecting each 
block-tower with the next tower on each side of it. 

(3) A line or wire called the message wire, and used for local 
traffic or business. 

The general arrangement of the block-tower is shown in 
Fig. 53. 

Each of the block-towers is sufficiently elevated above the 
road-bed to afford the operator an unobstructed view of the 
tracks. 

The operator, having ascertained the actual condition of the 
track either by observation, or by telegraphic communica- 
tion with the stations on either side of him, gives notice of 
this condition to all trains passing his station by the display 
of certain semaphore signals. 

The semaphore signals as used on this road are shown on 
following pages, in Figs, fit and 55. The form shown in Fig. 
54 is used in the absolute system, and that shown in Fig. 55 in 
the permissive system. These signals consist essentially oi 
an upright support provided with a movable arm A B, called 
the semaphore arm, capable of being set in any of two. or three 
positions. The semaphore signal is placed outside the 
signal tower, often several hundred feet away, but is 
readily set from the tower in any of the desired positions by 
the operator, by the movement of rods connected with levers. 

The semaphore arm can, in the permissive system, be set in 
three positions, viz.: 

(1) In a horizontal position, or where the semaphore arm 
makes an angle of 90° with the upright. 



78 



A DICTIONARY OF ELECTRICAL 



(2) Or it may be dropped down from the horizontal position 
through an angle of 75°, as shown in Fig. 54. 

(3) Or it may occupy a position exactly intermediate be- 







Fig. 5k. 



tween the first and the second, or 37° 30' below the horizontal, 
as shown in Fig\ 55. 



WORDS, TERMS AND PHRASES. 



79 



Position No. 1, is the clanger signal, and when it is displayed 
ihe train may not enter the block it governs. 




Fig. 55. 

Position No. 2 shows that the track is clear, and that the 
train may safely enter the block it governs. 
Position No. 3, which is used in the permissive block system 



80 A DICTIONARY OP ELECTRICAL 

only signifies caution, and permits the train to cautiously 
enter the block and look out for further signals. 

The semaphore arm consists of a light wooden arm, 11 
inches wide by 5}£ feet in length, painted red, or other 
suitable color that can be easily distinguished by daylight. 

By night the positions of the semaphore arm are indicated 
by colored lights. These lights are operated as follows ; viz., 
in the absolute system, the semaphore arm A B, pivoted at 
A, hears at its shorter end a disc or lens of red glass R, and, 
in the permissive system, below this another disc or lens of 
green glass G. An oil lantern, provided with an uncolored 
glass lens, is so supported on a bracket fastened to the up- 
right that when the semaphore arm points to danger, the red 
glass is immediately in front of the lantern ; when it points to' 
caution, the green glass is in front of the lantern; but 
when it points t.» safety, the lantern is left uncovered save 
by its uncolored glass. 

At night, therefore, when the semaphore arm is set to 
danger, a red light is displayed ; when it points to caution, a 
green light is displayed ; and when it points to safely, a white 
light is displayed. 

The green light is onty used in the permissive block system. 
In the absolute block system, the semaphore arm has two 
positions only ; viz., danger, or horizontal, and safety, or 75° 
below the horizontal. 

A single arm is used when it is intended to govern a single 
track only. Where the condition of a number of tracks is to 
be indicated, several arms are employed, one above the other. 

When semaphore signals are placed on each side of a double- 
track road, the semaphore arm pointing' to the right of the 
vertical support governs the line running to the right. 

When the semaphore signals are placed at junctions or 
switch-crossings, the operator in the signal-tower opens or 
closes the switches from the tower by the movements of 
levers that set the switches, and then displays the proper 



WORDS, TERMS AND PHRASES. 81 

semaphore signal for that crossing or route, red, or danger, if 
the route is blocked, and white, or safety, if it is clear. Here 
the interlocking apparatus is employed, which consists in a 
device by means of which, when a route has once been set up 
and a signal given for that route, the switches and signals are 
so interlocked that no signal can possibly be given for a con- 
flicting route. 

The signals or switches are operated by means of iron rods 
passing over rollers or pulleys. These rods are attached by 
suitable connections to the switch or semaphore signals, and 
are operated by means of levers from the signal -tower. 
Switches can be operated as far as 1,000 feet from the lower ; 
signals as far as 2,500 feet. 

Colored switch-signals are placed opposite the end of the 
switches to indicate the positions of the switch. These sig- 
nals consist of red and white discs for day, and a lantern pro- 
vided with red and white glasses for night. When the switch 
on any line is open, the switch-signal shows red ; when shut, 
it shows white. These switch-signals are only used in the 
yards. 

No passenger train is permitted on a block, after another 
train has passed the signal station, until a dispatch has been 
received from the station ahead that the train has passed and 
the block is thus cleared. 

As an additional precaution against rear collisions, tail- 
lights are displayed at the ends of the trains. These consist 
of lanterns placed on each side of the rear end of the last 
car. These lanterns are furnished with three glass slides. 
The side of the lantern towards the rear of the car shows a 
red light ; that to the front and side of the car shows a green 
light. The engineer, looking out of the cab, can thus see a 
green light, which serves as a " marker" and indicates to him 
that his train is intact. By day a green flag, placed in the 
same position as the lantern, serves the same purpose as a 
marker. An observer on the track, or in the tower, sees the 
red lights on the rear of the train when it has passed. 



A DICTIONARY OF ELECTRICAL 




Freight trains are now run on separate tracks, except 
in places where the extra tracks are not yet completed. 
Here they do not run on schedule time, but are permitted to 
follow one another at intervals that depend on the condition 
of the tracks as shown by the signals displayed. 

Blow-Pipe, Electric A blow-pipe in which the 

p P air-blast is supplied 

by the stream of air 
pari i cles produced 

Q /^^ + Hi*" a ^ *- ne P om ^ of a 

charged conductor 
by the convection 
discharge. 

The candle flame 
Fig. 56, is blown 
in the direction 
shown by the stream 
Fig - 56, of air particles pass- 

ing off from the point P. (See Convection, Electric.) 

IS low- Pipe, Electric Arc — — A device of Wer- 

dermann for cutting rocks, or other refractory substances, in 
which the heat of the voltaic arc is directed by means of a 
magnet, or blast of air, against the substance to be cut. 

The carbons are placed parallel, so 
as to readily enter the cavity thus cut 
or fused. This invention has never 
been introduced into extensive prac- 
tice. 

As shown in Fig. 57 the voltaic arc, 
taken between two vertical carbon elec- 
trodes, is deflected into a horizontal posi- 
tion under the influence of the inclined 
poles of a powerful electro-magnet. 

The highly heated carbon vapor that Fig - 57 ' 

constitutes the voltaic arc is deflected by the magnet in 




WORDS, TERMS AND PHRASES. 8S 

the same direction as would be any other movable circuit or 
current. 

Board, Multiple Switch A board to which the 

numerous circuits employed in systems of telegraphy, tele- 
phony, annunciator, or electric light and power circuits, are 
connected. 

Various devices are employed for closing- these circuits, or 
for connecting, or cross-connecting, them with one another, 
or with neighboring circuits. 

A multiple switch board, for example, for a telephone 
exchange, will enable the operator to connect any subscriber 
on the line with any other subscriber on that line, or on 
another neighboring line provided with a multiple switch- 
board. To this end the following - parte are necessary: 

(1) Devices whereby each line entering the 
exchange can readily have inserted in its circuit 
a loop connecting it with another line. This 
is accomplished by placing on the switch- 
board a separate spring-jack connection for 
each separate line. Tins connection consists 
essentially of one o\- two springs made of any 
conducting metal, which are kept in metallic 
contacl but which can be separated from one Fig.rs. 
another by the introduction of the plug key, Fig. 58, the 
terminals, a and 6, of which are insulated from each other, and 
are connected to the ends of a. loop coming from another line. 
As the key is inserted, the metallic spring or springs of the 
spring-jack are separated, and the metallic pieces, a and b. 
brought into good sliding contact therewith, thus introducing 
the loop into the circuit. (See Spring-Jack.) 

(2) As many separate Annunciator Drops as there are separate 
subscribers. These are provided so as to notify the Central 
Office of the particular subscriber who desires a connection. 
Alarm-bells, to call the operator's attention to the calling 




84 A DICTIONARY OF ELECTRICAL 

subscriber, or to the falling of a drop, are generally added. 
(See Annunciators. Bell Call, Electric.) 

(3) Connecting Cords and Keys for connectiong the opera- 
tor's telephone, and means for ringing subscribers' bells, and 
clearing out drops. 




Fig. 



In Electric Light Switch-Boards, or Distributing Switches, 
spring-jack contacts are connected with the terminals of dif- 
ferent circuits, and plug-switches with the dynamo terminals. 
By these means, any dynamo can be connected with airy cir- 
cuit, or a number of circuits can be connected with the same 
dynamo, or a number of separate dynamos can be placed 
in the same circuit, without interference with the lights. 



WORDS, TERMS AND PHRASES. 



85 



Boat? Electric A boat provided with electric mo- 
live power. 

Electric power has been applied both for ordinary vessels 
and for sub-marine torpedo boats. 

Bobbins, Electric An insulated coil of wire for 

an electromagnet. (See Coils, Elect fie.) 

Body Protector, Electric A device for pro 

tecting the human body against the accidental passage of 




Fig. 60. 
for automat i< - 



To protect the human body from the acci- 
dental passage through it of dangerous elec- 
tric currents, Dclany places alight, flexible, 
conducting wire, A A B L L, in the posi- 
tion shown in Fig, 00, for the purpose of 
leading the greater part of the current 
around instead of through the body. 

Inside insulating shoe-soles for lessen- 
ing the danger from accidental contacts 
through grounded circuits have also been 
proposed. 

Boiler-Feed, Electric A device 

ally opening a boiler-feed apparatus electrically, when the 
water in the boiler falls to a certain predetermined point. 

Bole. — A unit recently proposed by the British Associa- 
tion. 

One bole is equal to oue gramme-kine. 

Bolometer, or Langlcy's Thermic Balance.— An 

apparatus for determining small differences of temperature, 
constructed on the principle of the differential galvanometer. 
(See Galvanometer, Differential.) 

A coil composed of two separate insulated wires, wound to- 
gether, is suspended in a magnetic field, and has a current sent 
through it. Under normal conditions, this current separates 
into two equal parts, and runs through the wires in opposite 



86 A DICTIONARY OF ELECTRICAL 

directions. It therefore produces no sensible field, and suffers 
no deflection by the field in which it is suspended. 

Any local application of heat, however, causing- a difference 
in resistance, prevents this equality. A field is therefore pro- 
duced in thr suspended coil, which, though extremely small, 
is rendered measurable by menus of the powerful field pro- 
duced in the coil, within which the double coil is suspended. 

Differences of temperature as small as- degree F. are 

detected by the instrument. 

ISoinhai 'tlmciit, Molecular- The forcible rec- 
tilinear projection of molecules in exhausted vessels, that 
takes place from the negative (electrode, on the passage of 
electric discharges. (See Matter, Radiant.) 

Boreal Magnet I'olc. — A namesometimes employed in 
France for the south-seeking pole of a magnet, as distin- 
guished from the austral, or north-seeking pole. 

That pole of a magnet which points toward the geo- 
graphical south. 

If the earth's magnetic pole in the Northern Hemisphere be 
of north magnetism, then the pole of a needle that points to 
it must be of the opposite polarity, or of south magnetism. 
In this country we call the end winch points to the north the 
north-seeking end, or tin; marked pole. In France, the end 
which points to the north is called the austral pole. Austral 
means south pole. (Sec Austral Magnet Pole.) 

The austral is therefore the north-seeking pole, and the 
boreal, the south-seeking pole. 

ISouelierizing. — A process adopted for the preservation 
of wooden telegraph poles, by injecting a solution of copper 
sulphate into the pores of the wood. (See Poles, Telegraphic.) 

Sound and Free Charge. — The condition of an elec- 
tric charge on a conductor placed near another conductor, 



WORDS, TERMS AND PHRASES. 



87 



but separated from it by a medium through which electro- 
static induction can take place. (See Induction, Electrostatic.) 

The charge, on a completely isolated conductor, readily 
leaves it when put in contact with a good conductor con- 
nected with the ground. The charge in this condition is 
called a, free charge. When, however, the conductor is placed 
near another conductor, but separated from it by a medium 
through which induction can take place, a charge of the oppo- 
site name is induced in the neighboring conductor. This 
charge is held or bound on the conductor by the mutual at- 
traction of the opposite charges. 

To discharge a bound charge, both conductors must be sim- 
ultaneously touched by any good conducting substance. The 
bound charge was formerly called dissimulated or latent elec- 
tricity. (See Charge. Dissimulated or Latent Electricity.) 

Box Bridge. — (See Balance, Wheatstonc's Electric, Box 
Form of.) 



Box, Dislribiitioii- 



-for Electric Are fJylu 



Circuit*. — A device by means of which arc and incandescenl 
lights may be simultaneously employed on the same line, 
from a constant current dynamo electric-machine or othei 
source. 

A portion of the line circuit, whose difference of potential 
is suflicient to operate the electro-receptive device, as for ex- 
ample an incandescent lamp, is divided into such a number 
of multiple circuits as will provide a current of the requisite 
— +— 



* =* 

4= _^ * 

* — ± 

4= * 

* _ * 

± ) V ±. 



-* — 



Fig. 61. 

strength for each of the devices. In order to protect the re- 
maining of these devises so interpolated, on the extinguish- 
ment of any of the devices, automatic cut-outs are provided 



oo A DICTIONARY OF ELECTRICAL 

which divert the current thus cut off through a resistance 
equivalent to that of the device. 

A variety of distribution boxes are in use. 

The character of circuit employed in connection with dis- 
tribution boxes is shown in Fig. 61. (See Circuits, Varieties 
of.) 

Box, Resistance A box containing- a number of 

standardized resistance coils. 

The resistance box and coils are of the same general con- 
struction as the Box Bridge. (See Balance, Wheatstone's 
Electric, Box Form of.) 

Bracket, Lamp A device for holding or sup- 
porting an electric lamp, similar to a bracket for a gas burner. 




B I «4 



«fcl 




Fig. 62. W Fi V- 63 - 




Fig. 6h. 

Lamp brackets are either fixed or movable. Those shown 
in Figs. 62 and 63 are fixed. That shown in Fig. 64 is mov- 
able. 

Brackets, Telegraphic or Arms.— The sup- 
ports or cross pieces on telegraph poles, provided for the 
insulators of telegraphic lines. 



WORDS, TERMS AND PHRASES. 



Telegraphic insulators are supported either on wooden arms, 
or on iron or metal brackets. 





Fig. 65. 

Fig. 65, shows a form of iron bracket. Fig. 66, shows a 
form of wooden arm. 

Various well known modifications of these shapes are in 
common use. For details see Telegraph Poles. 

Brake, Electro-Magnclic A brake for car 

wheels, the braking powers for which is either derived from 
electro-magnetism, or is thrown into action by electro-mag- 
netic devices. 

Electro-magnetic car brakes are of a great variety of forms. 
They may, however, be arranged in two classes, viz. : 

(1) Those in which magnetic adhesion or the magnetic at- 
traction of the wheels to the brake is employed. 

(2) Ordinary brake mechanism in which the force operating 
the brake is thrown into action by an electro-magnet. 

Brake. Prony or Friction A mechanical de- 
vice for measuring the power of a driving shaft. 



90 



A DICTIONARY OF ELECTRICAL 



An inflexible beam, Fig. 67, is provided at one end with a 
clamping- device for clamping the driving shaft, and at the 
other end A, with a pan for holding weights. 

If the brake be arranged as 
shown in Fig. 67, and the 
shaft rotate in the direction 
of the arrow, the tendency is 
to carry the beam around with 
it, placing it at one moment 
in the position shown by the 



qa? 



5 



M. 




Fig. 67 

dotted line. If a sufficiently heavy 
weight be placed at x, in a pan 
hung at A, the beam will assume 
a vertical position downwards. 
If, however, the torque, or twist- 
ing force of the driving shaft be 
balanced by the weight, the bar 
will remain horizontal. The 
power can then be calculated by 
multiplying the weight in pounds 

5 V 



Sg^J 





w 



z> 



A 



Fig. 68. 

by the circumference in feet 
of the circle of which the bar is 
a radius, and tin's product by the 
number of turns of the driving 
shaft per minute. The product 
will be the number of foot- 
pounds per minute, and, when 
divided by 33,000, will give the 



Fig. 69. 
Horse-Power. (See Horse-Poiver.) 

Some modified forms of the Prony Brake are shown in Figs. 
68, and 69. 

Branch -Block. — A device employed in electric wiring 
for taking off a branch from a main circuit. 

Breaking Weight of Telegraph Wires.— The 
weight which when hung at the end of a wire will break it. 



WORDS, TERMS AND PHRASES. 



91 



Ordinary copper wire will break at about 17 tons to the 
square inch of cross-section. Common wrought iron breaks at 
25 tons to the square inch. When drawn, the breaking weight 
is often as great as 40 or 50 tons to the square inch. These 
figures are to be regarded as approximate only, since differ- 
ences in the physical conditions of metals, as well as slight 
variations in their chemical composition, often produce marked 
differences in their breaking weights. 

Breath Figures, Electric (See Figures, Elec- 
tric or Breath.) 

Bridge, Electric (See Balance, Wkeatstone's 

Electric) 

Bridge, magnetic An apparatus invented by 

Edison for measuring magnetic resistance, similar in principle 
to Wheatstone's Electric Bridge. 




Fig. 70. 

The magnetic bridge is based on the fact that two points at 
the same magnetic potential fail, when connected, to produce 
any action on a magnetic needle. The magnetic bridge may 
be arranged as shown in Fig. 70, of four sides made of pure, 
soft iron. The poles of an electro-magnet are connected, as 
shown, to projections at the middle of the short side of the 
rectangle. By this means a difference of magnetic potential is 



92 A DICTIONARY OF ELECTRICAL 

maintained at these points. The two long sides are formed 
of two halves each, which form the four arms of the balance. 
Two of these only are movable. 

Two curved bars of soft iron, of the same area of cross-sec- 
tion as the arms of the bridge, rest on the middle of the long- 
arms, in the arched shape shown. Then- ends approach near 
the top of the arch within about a half inch. A space is hol- 
lowed out between these ends, for the reception of a short 
needle of well-magnetized hardened steel, suspended by a wire 
from a torsion head. 

The movements of the needle are measured on a scale by a 
spot of light reflected from a mirror. 

The electro-magnet maintains a constant difference of mag- 
netic potential at the two shorter ends of the rectangle. If, 
therefore, the four bars, or arms of the bridge, are magneti- 
cally identical, there will be no deflection, since no difference 
of potential will exist at the ends of the bars between which 
the needle is suspended. If one of the bars or arms, how- 
ever, be moved even a trifle, the needle is at once deflected, 
I he motion becoming a maximum when the bar is entirely re- 
moved. If replaced by another bar, differing in cross-section, 
constitution, or molecular structure, the balance is likewise 
disturbed. 

The magnetic bridge is very sensitive. It was designed 
by its inventor for testing the magnetic qualities of the iron 
used in the construction of dynamo-electric machines. 

Bridge, Whcatstoiic's Electric (See Wheat- 
stone's Balance, Electric.) 

Broken Circuit. — An open circuit. 

A circuit, the electrical continuity of which has been broken, 
and through which the current has therefore ceased to pass. 

Broken Circuit. — (See Circuit, Broken.) 

Brush Discharge The faintly luminous dis- 
charge that occurs from a pointed positive conductor. (See 
Discharge, Convective.) 



WORDS, TERMS AND PHRASES. 



98 



■An electrode in the form of a 



Brush, Faradic 

brush employed in the medical application of electricit} 7 . 
The bristles are generally made of nickelized copper wire. 

Brusli Holders for Dynamo-Electric Machines. 

— Devices for supporting the collecting brushes of dynamo- 
electric machines. 

As the brushes require to be set or placed on the commu- 
tator in a position which often varies with the speed of the 
machine, and with changes in the external circuit, all brush 
holders are provided with some device for moving them con- 
centrically with the commutator cylinder. 

Brushes, Adjust in cut of tlie of Dynamo- 

Electric Machines. — Shifting the brushes into the required 
position on the commutator cylinder, either non-automatically 
by hand, or automatically by the current itself. (See Auto- 
matic Regulation of Dynamo-Electric Machines.) 

Brushes for Dynamo-Electric Machines.— Strips 
of metal, bundles of wire, or slit plates of metal, or carbon, 
that bear on the commutator cylinder 
and carry off the current generated. 

Rotating brushes consisting of metal 
discs are sometimes employed. Copper 
is almost universally used for the 
brushes of dynamo-electric machines. 

The brush shown at B, Fig. 71, is 
formed of copper wires, soldered to- 
gether at the non-bearing end. A cop- 
per plate, slit at the bearing end, is 
shown at C, and bundles of copper 
plates, soldered together at the non- 
healing end, are shown at D. 

The brushes should bear against the 
commutator cylinder with sufficient 
force to prevent jumping, and conse- Fir/. 71. 

quent burning, and yet not so hard as to cause excessive wear. 




94 



A DICTIONARY OF ELECTRICAL 



Brushes, Lead of The angle through which 

the brashes of a dynamo-electric machine must be moved for- 
wards, or in the direction of rotation, in order to diminish 
sparking and to get the best output from ihe dynamo. 

The necessity for the lead arises from the counter magnetism 
of the armature, and the magnetic lag of its iron core. (See 
Angle of Lead.) 



Brushes, Scratch 



Brushes made of wire or stiff 

cleaning the surfaces of metallic 



bristles, etc., suitable for 

objects before placing them in the plating bath. 

These brushes are of various shapes and are provided with 
wires or bristles of varying coarseness. 

Buoy, Electric A buoy, on which luminous 

electric signals are displayed. 
Bunseii's Voltaic Cell.— (See Cell, Voltaic.) 

Burner, Electric A gas- 
burner whose gas-jet is electrically ignited. 
On pulling the pendant C, Fig. 72, a spark 
from a spark coil ignites the gas. On pull- 
ing the slide the gas is turned off. (See 
Argand Burner.) 

Burner, Automatic Electric 

— An electric device for either turning on 
the gas and lighting it, or for turning it off. 
One push-button, usually a white one, 
turns the gas on and lights it by means of 
a succession of sparks from a spark coil. 
Another push-button, usually a black one, 
turns the gas off. Automatic burners are 
Fig. 72. also made with a single button. 

Burglar Alarm.— (See Alarm, Electric, Burglar.) 
Burnetizing. — A method adopted for the preservation of 
wooden telegraph poles by injecting a solution of zinc chlor- 
ide into the pores of the wood. (See Poles, Telegraphic.) 




WORDS, TERMS AND PHRASES. 



95 



Burning at Commutator of Dynamo.— An arcing 

at the brushes of a dynamo-electric machine, due to their im- 
perfect contact, or improper position, which results in loss of 
energy and destruction of the commutator segments. 

Butt Joint.— (See Joint, Butt.) 

Button, Pu§li A device for closing an electric 

circuit by the movement of a button. 

A button, when pushed by the hand, closes a contact, and 
thus completes a circuit in which some electro-receptive device 
is placed. This circuit is opened by a spring, on the removal 
of the pressure. Some forms of push-buttons are shown in 
Figs. 73 and 73a. 





Fig. 73, 



Fig. lh. 



A floor-push for dining-rooms and offices is shown in Fig. 
74. 

B. W. O. — A contraction for Birmingham Wire Gauge. 
(See Wire Gauge.) 

Buzzer, Eleetrie A call, not as loud as that of a 

bell, produced by an automatic make and break. (See 
Alarms. Electric.) 

Cable Armor— (See Armor of Cable.) 
Cable Clip.— (See Cable Hanger.) 



96 



A DICTIONARY OF ELECTRICAL 



Cable Core.— (See Core of Cable.) 

Cable, Aerial —A cable for telegraphic or tele- 



the 



from suitable 



phonic communication, suspended 
poles. 

Cable, Electric A conductor containing either 

a single conductor, or two or more separately insulated 
electric conductors. 

Strictly speaking, the word cable should be limited to the 
case of more than a single conductor. Usage, however, 
sanctions the employment of the word to indicate a single 
insulated conductor. 

The conducting wire may consist of a single wire, of a 
number of separate wires electrically connected, or of a num- 
ber of separate wires insulated from one another. 

An electric cable con- 
sists of the following 
parts, viz. : 

(1) The conducting 
wire or core. 

(2) The insulating 
material for separating 
the several wires, and 

(3) An armor or pro- 
tecting covering, con- 
sisting of strands of iron 
wire, or of a metallic 
coating or covering of 
lead. 

As to their position, 
cables are, aerial, sub- 
marine, or under- 
ground. As to their 
purpose, they are tele- 
graphic, telephonic, or electric light and power cables. 

Fig. 75 shows a form of submarine cable in which the armor 
is formed of strands of iron wire. 








WORDS, TERMS AND PHRASES. 97 

Cablegram.— A message received by means of a sub- 
marine telegraphic cable. 

Cable Hanger.— A hanger or hook, suitably secured to 
the cable, and designed to sustain its 
weight by intermediately supporting it 
on iron or steel wires. 

A cable hanger, or cable clip, is 
shown in Fig. 76. 

The weight per foot of an aerial cable 
is generally so great that the poles or 
supports would require to be very near 
together, unless the device of inter- 
mediate supports, by means of cable ,* 
clips, were adopted ff 

Cable Serving. — Strands of tarred 
hemp or jute, wrapped around the in- Fig. 76. 

sulated core of a cable, to protect it from the pressure of the 
metallic armor. 

Cables, Submarine Cables designed for use 

under water. 

These are either shallow -water, or deep-sea, cables. Gutta- 
percha answers admirably for the insulating material of the 
core. Various other insulators are also used. 

Strands of tarred hemp or jute, known as the cable-serving, 
are wrapped around the insulated core, to protect it from the 
pressure of the galvanized iron wire armor afterwards put on. 
To prevent corrosion of the iron wire, it is covered with tarred 
hemp, galvanized, or otherwise coated. 

Cables, Underground Cables designed for use 

underground. 

These are either placed directly in the ground, or in coiu 
ditits, or subways, especially prepared to receive them. (See 
Conduit, Electric Underground. Subway, Electric.) 

Calibration, Absolute and Relative of In- 
strument. — The determination of the absolute or the rela- 



98 A DICTIONARY OF ELECTRICAL 

tive values of the reading of an electrometer, galvanometer, 
voltmeter, amperemeter, or other similar instrument. 

The calibration of a galvanometer, for example, consists in 
the determination of the law that governs its different de- 
flections, and by which is obtained in amperes, either the ab- 
solute or the relative current required to produce such 
deflections. 

For various methods of calibration, see standard works on 
Electrical Testing, or on Electricity. 

Calibration, Invariable of Galvan- 
ometer. — In galvanometers with absolute calibration, a 
method for preventing the occurrence of variations in the in- 
tensity of the field of the galvanometer, due to the neighbor- 
hood of masses of iron, etc. 

Callaud Voltaic Cell.— (See Cell, Voltaic.) 

Call-Bell, Electric (See Alarm, Electric. Belt- 
Call, Electric.) 

Caloric. — A term formerly applied to the fluid that was 
believed to be the cause or essence of heat. 

The use of the word caloric at the present time is very 
unscientific, since heat is now known to be an effect and not a 
material thing. (See Heat.) 

Calorie, or Calory. — A heat unit. 

There are two calories, the small and the large calorie. 

The amount of heat required to raise the temperature of one 
gramme of water, 1° C. is called the small calorie. 

Sometimes the term is used to mean the amount of heat 
required to raise 1,000 grammes of water 1° C. This is called 
the large calorie. The first usage of the word is the com- 
monest. 

Calorescence. — The transformation of invisible heat-rays 
into luminous rays, when received by certain solid substances. 

The term was proposed by Tyndall. The light and heat 
from a voltaic arc are passed through a hollow glass lens 
filled with a solution of iodine in bisulphide of carbon. 



WORDS, TERMS AND PHRASES. 99 

This solution is opaque to light but quite transparent to 
heat. 

If a piece of charred paper, or thin platinum foil, is placed 
in the focus of these invisible rays, it will be heated to brilliant 
incandescence. (See Focus.) 

Calorimeter. — An instrument for measuring- the quan- 
tity of heat possessed by a given weight or volume of a body 
at a given temperature. 

Thermometers measure temperature only. A thermometer 
plunged in a cup full of boiling water shows the same temper- 
ature that it would in a tub full of boiling water. The quantity 
of heat present in the two cases is of course greatly different 
and can be measured by calorimeters only. 
Various forms of Calorimeters are employed. 
In order to determine the quantity of heat in a given 
weight of any body, this weight may be heated to a definite 
temperature, such as the boiling point of water, and placed in a 
vessel containing ice, and the quantity of ice melted by the 
body in cooling to the temperature of the ice, is determined 
by measuring the amount of water derived from the melting 
of the ice. Care must be observed to avoid the melting of the 
ice by external heat. 

In this way the amount of heat required to raise the tem- 
perature of a given weight of a body a certain number of de- 
grees, or the capacity of the body for heat, may be compared 
with the capacity of an equal weight of water. This ratio is 
called the Specific Heat. (See Heat, Specific.) 

The heat energy, present in a given weight of any substance 
at a given temperature, can be determined by means of a 
calorimeter ; for, since a pound of water heated 1° F. absorbs 
an amount of energy equal to 772 foot-pounds, the energy can 
be readily calculated if the number of pounds of water and the 
number of degrees of temperature are known. (See Me- 
chanical Equivalent of Heat.) 



100 



A DICTIONARY OF ELECTRICAL 



Calorimeter, Electric 

uring the heat developed in a conductor 
an electric current. 



An instrument for meas- 
in a given time, by 



A vessel containing water, is 
provided with a thermometer T, 
Fig. 77. The electric current 
passes for a measured time 
through a wire N M, immersed 
in the liquid. 

The quantity of heat is deter- 
mined from the increase of 
temperature, and the weight of 
the water. 

According to Joule, the num- 
ber of heat units (See Heat Un- 
Fi &- 77 - its, English) developed in a con- 

ductor by an electric current is proportional, 

1. To the Resistance of the Conductor. 

2. To the Square of the Current passing. 

3. To the Time the current is passing. 

The heating power of a current is as the square of the cur- 
rent only when the resistance remains the same. (See Heat, 
Electric.) 

Calorimetric Photometer.— (See Photometer, Calori- 
metric. ) 




Candle, Elcctric- 



-A term applied to the Jab- 



lochkoff candle, and other similar devices. 

The Jabiochkoff electric candle consists of two 
parallel carbons, separated by a layer of kaolin 
or other heat-resisting' insulating material, as 
shown in Fig. 78. The current is passed into 
and out of the carbons at one end of the candle, 
and forms a voltaic arc at the other end. In 
order to start the arc, a thin strip called the igniter, 
consisting of a mixture of some readily ignitable 
substance, connects the upper ends of the carbons. 




WORDS, TERMS AND PHRASES. 101 

An alternating current is generally employed with these 
candles, thus avoiding the difficulty which would otherwise 
occur from the more rapid consumption of the positive than 
the negative carbon. (See Current, Alternating.) 

Candle, Foot A unit of illumination equal to 

the illumination produced b}* a standard candle at the distance 
of one foot. Proposed by Hering. 

According to this unit, the illumination produced by a stand- 
ard candle at the distance of two feet would be but the one- 
fourth of a foot-candle ; at three feet, the one-ninth of a foot- 
candle, etc. 

The advantage of the proposed standard lies in the fact 
that knowing the illumination in foot-candles required for the 
particular work to be done, it is easy to calculate the position 
and intensity of the lights required to produce the illumina- 
tion. 

Candie, Metre — The illumination produced by 

a standard candle at the distance of one metre. 

Candle, Standard A candle of definite compo- 
sition which, with a given consumption in a given time, will 
produce a light of a fixed and definite brightness. 

A candie which burns 120 grains of spermacetti wax per 
hour, or 2 grains per minute, will give an illumination equal 
to one standard candle. 

Candle. A , or, Unit of Photometric Meas- 

nremciit. — The unit of photometric intensity. 

Such a light as would be produced by the consumption of 
two grains of a standard candle per minute. 

An electric lamp of 16 candle-power, or one of 2,000 candle- 
power, is a light that gives respectively 16 or 2,000 times as 
bright a light as that of one standard candle. 

Capacity, Dielectric (See Dielectric Capacity.) 

Capacity, Electro§tatic The ability of a con- 



102 A DICTIONARY OF ELECTRICAL 

ductor or condenser to hold a certain quantity of electricity 
at a certain potential. 

The electrostatic capacity of a conductor, or of a condenser, 
is measured by the quantity of electricity which must be given 
it as a charge, in order to raise its potential a certain amount. 
(See Condenser. Potential.) In this respect the electrostatic 
capacity of a conductor is not unlike the capacity of a vessel 
filled with a liquid or gas. A certain quantity of liquid will 
fill a vessel to a level dependent on the size or capacity of the 
vessel. In the same manner a given quantity of electricity 
will produce, in a conductor or condenser, a certain difference 
of electric level dependent on the electrical capacity of the con- 
ductor or condenser. 

Or, the quantity of gas that can be forced into a vessel de- 
pends on the size of the vessel and the pressure with which it 
is forced in. A tension or pressure is thus produced by the 
gas on the walls of the vessel that is greater, the smaller the 
size of the vessel, and the greater the quantity forced in. 

In the same manner, the smaller the capacity of a conduc- 
tor, the smaller is the charge required to raise it to a given 
potential, or the higher the potential a given charge will 
raise it. 

The capacity K, of a conductor or condenser, is therefore 
directly proportional to the charge Q, and inversely propor- 
tional to the potential V, or 

Q 

K =- . 
V 

From which we obtain Q = KV; or, 

The quantity of electricity, required to charge a conductor 
or condenser to a given potential, is equal to the capacity of 
the conductor or condenser multiplied by the potential through 
which it is raised. 

Capacity, Electrostatic Unit of ; The 

Farad. — A conductor or condenser of such a capacity that 



WORDS, TERMS AND RHRASES. 103 

an electro-motive force of one volt will charge it with a quan- 
tity of electricity equal to one coulomb. (See Farad.) 

Capacity of Polarization of a Voltaic Cell.— The 
quantity of electricity required to be discharged by a voltaic 
cell in order to produce a given polarization. (See Cell, Vol- 
taic. Polarization of Negative Plate.) 

During the discharge of a voltaic battery, an electro-motive 
force is gradually set up that is opposed to that of the battery. 
The quantity of electricity required to produce a given polariza- 
tion, depends, of course, on the condition and size of the 
plates. Such a quantity is called the Capacity of Polarization. 

Capacity of a Telegraph Line or Cable.— The 
ability of a wire or cable to permit a certain quantity of elec- 
tricity to be passed into it before acquiring a given difference 
of potential. 

Before a telegraph line or cable can transmit a signal to 
its further end, its difference of potential must be raised to a 
definite amount dependent on the character of the instru- 
ments and the nature of the system. 

The first effect of a given quantity of electricity being 
passed into a line, is to produce an accumulation of electricity 
on the line, similar to the charge in a condenser. Cables 
especially act as condensers, and from the high specific induc- 
tive capacity of the insulating materials employed, permit 
considerable induction to take place between the core, and 
the metallic armor or sheathing, or the ground. 

The capacity of a cable depends on the capacity of the 
wire ; i.e., on its length and surface, on the specific inductive 
capacity of its insulation, and its neighborhood to the earth, 
or to other conducting wires, casings, armors, or metallic 
coatings. Submarine or underground cables therefore have 
a greater capacity than air lines. 

This accumulation of electricity produces a retardation in 
the speed of signaling, because the wire must be charged be- 
fore the signal is received at the distant end, and discharged 



104 



A DICTIONARY OF ELECTRICAL 



or neutralized before a current can be sent in the reverse 
direction. This latter may be done by connecting- each end to 
earth, or by the action of the reverse current itself. 

The smaller the electrostatic capacity of a cable, therefore, 
the greater the speed of signaling. (See Retardation.) 

Capacity, Specific Inductive ; Dielectric 

Capacity, or Dieletric Constant.— The ability of a dielec, 
trie to permit induction to take place through its mass, as 
compared with the ability possessed by a mass of air of the 
same dimensions and thickness, under pre- 
cisely similar conditions. 

The inductive capacity of a dielectric is 
compared with that of air. 

According- to Gordon and others, the 
specific inductive capacities of a few sub- 
stances compared with air, are as follows : 

Air. ...1.00 

Glass 3.013 to 3.258 

Ebonite 2.284 

Gutta-percha 2.462 

India rubber 2.220 to 2.497 

Paraffin (solid) 1.994 

Shellac 2.740 

Sulphur 2.580 

Turpentine 2.160 

Petroleum 2.030 to 2.070 

Carbon bisulphide 1.810 

Vacuum 0.99941 

Hydrogen 0.99967 

Carbonic acid... 1.00036 




Fig. 70. 



Faraday, who proposed the term specific inductive capac- 
ity, employed in his experiments a condenser consisting- of 
a metallic sphere A, Fig. 79, placed inside a large hollow 
sphere B. 



WORDS, TERMS AND PHRASES. 



105 



The concentric space between A and B was filled with 
the substance whose specific inductive capacity was to be de- 
termined. 

Capillarity. — The elevation or depression of liquids in 
tubes of small internal diameter. 

The liquid is elevated when it wets the walls, and depressed 
when it does not wet the walls of the tube. 

The phenomena of capillarity are due to the molecular at- 
tractions existing- between the molecules of the liquid for one 
another, and the mutual attraction between the molecules of 
the liquid and those of the walls of the tube. 

Capillarity, Effects of, on Battery Cells.— Disturb- 
ing- effects of the proper action of a voltaic battery caused by 
capillary action. 

These effects are as follows, viz. : 

(1) Creeping, or Efflorescence of salts. (See Creeping. 
Efflorescence.) 

(2) Oxidation of Contacts and consequent introduction of 
increased resistance into the battery circuit. The liquid enters 
the capillary spaces between the contact surfaces and oxidizes 
them. 

Capillary Eleetrometer. — An electrometer in which 




Fig 



difference of potential is measured by the movements of a drop 
of sulphuric acid in a horizontal tube filled with mercury. 
The horizontal glass tube with a drop of acid at B, is shown in 



106 a Dictionary oe electrical 

Fig. 80. The ends of the tube are connected with two vessels, 
M and N, filled with mercury. If a current be passed through 
the tube, a movement of the drop toivards the negative pole 
will be observed. Where the electro-motive force does not 
exceed one volt, the amount of the movement is proportional 
to the electro-motive force. 

Carbon. — An elementary substance which occurs naturally 
in three distinct alio tropic forms, viz. : charcoal, graphite and 
the diamond. (See Allotropy.) 

Carbon, Artificial Carbon obtained by the car- 
bonization of a mixture of pulverized carbon with different 
carbonizable liquids. 

Powdered coke, or gas-retort carbon, sometimes mixed with 
lamp-black or charcoal, is made into a stiff dough with 
molasses, tar, or any other hydro-carbon liquid. The mixture 
is moulded into rods, pencils, plates, bars or other desired 
shapes by the pressure of a powerful hydraulic press. After 
drying, the carbons are placed in crucibles and covered with 
lamp-black, or powdered plumbago, and raised to an intense 
heat at which they are maintained for several hours. By the 
carbonization of the hydro-carbon liquid the carbon paste be- 
comes strongly coherent, and by the action of the heat its 
conducting power increases. 

To give increased density after baking, the carbons are 
sometimes soaked in a hydro-carbon liquid, and subjected to a 
re-baking. 

Carbon Electrodes for Arc Lamps. — Rods of artifi- 
cial carbon employed in arc lamps. 

Carbons for arc lamps are generally copper-coated, so as to 
somewhat decrease their resistance, and to ensure a more 
uniform consumption. They are sometimes provided with 
a central core of soft carbon, which fixes the position of 
the arc and thus ensures a steadier light. (See Carbons, 
Cored.) 



WORDS, TERMS AND PHRASES. 107 

Carbon Holders for Arc Lamps.— Various clamping- 
devices for holding the carbon electrodes of an arc lamp in the 
lamp rods. 

Carbon Telephone Transmitter.— A telephone 
transmitter consisting of a button of compressible carbon. 

The sound-waves impart their to-and-fro-movements to the 
transmitting diapraghm, and this to the carbon button thus 
varying its resistance by pressure. This button is placed in 
circuit with the battery and induction coil. (See Telephone.) 

Carbonic Acid Gas. — A gaseous substance formed by 
the union of one atom of carbon with two atoms of oxygen. 

Carbonic acid gas is formed by the combustion of carbon in 
a full supply of air. 

Carbonization, Processes of Means for suit- 
ably carbonizing carbonizable material. 

Carbonizable material is placed in suitably shaped boxes, 
covered with powdered plumbago or lamp-black, and subjected 
to the prolonged action of intense heat while out of contact 
with air. 

The electrical conducting power of the carbon which results 
from this process is increased by the action of the heat, and, 
probably, also by the deposit in the mass of the carbon, of 
carbon resulting from the subsequent decomposition of the 
hydro-carbon gases produced during carbonization. 

When the carbonization is for the purpose of producing' con- 
ductors for incandescent lamps, in order to obtain the 
uniformity of conducting power, electrical homogeneity, 
purity and high refractory power requisite, selected fibrous 
material, cut or shaped in at least one dimension prior to car- 
bonization, must be taken, and subjected to as nearly uniform 
carbonization as possible. 

Carbonized Cloth for High Resistances.— Discs of 

cloth carbonized by heating them to an exceedingly high tem- 
perature in a vacuum, or out of contact with air. 



108 



A DICTIONARY OF ELECTRICAL 



After carbonization the discs retain their flexibility and 
elasticity and serve admirably for high resistances. When 
piled together and placed in glass tubes, they form excellent 
variable resistances when subjected to varying pressure. 

Carbons, Cored for Arc Lamps.-A cylindri- 
cal carbon electrode that is moulded around a central core of 
charcoal, or other softer carbon. 

These carbons, it is claimed, render the arc light steadier, 
by maintaining the arc always at the softer carbon, and hence 
at the central point of the electrode. 

A core of harder carbon, or other refractory material, is 
sometimes provided for the negative carbon. 

Carbons, Concentric*, Cylindrical A cylin- 
drical rod of carbon placed inside a hollow cylinder of carbon 
but separated from it by an air space, or by 
some other insulating, refractory material. 

Someti nes Jablochkoff candles are made 
with a solid cylindrical electrode, concentri- 
cally placed in a. hollow cylindrical carbon. 

Carcel. — The light emitted by a lamp burn- 
ing 42 grammes of pure colza oil per hour, 
with a flame 40 millimetres in height. 
One carcel = 9.5 to 9.6 standard candles. 
Carcel Lamp. — An oil lamp employed in 
France as a photometric standard. 
Fig. 81 shows a form of carcel lamp. 
Carcel Standard Gas Jet.— A lighted 
gas jet employed for determining the candle 
power of gas by measuring the height of a jet 
of g»as burning under a given pressure, and 
used in connection with the light of a larger 
gas burner, burning under similar conditions, for the photo- 
metric measurement of electric lights. 




WORDS, TERMS AND PHRASES. 



109 



In Fig-. 82, is shown a section of a seven-carcel standard gas 
jet, and, in Fig. 83, a section of a " candle burner,"' connected 
with the same service pipe. The gas for both burners is re- 
ceived in a chamber 

from whence it passes v~_\ 

by an opening to the 
burner under the con- 
stant pressure obtained 
by the weight of the 
bell C, and the tube A. 
The burner shown in 
Fig. 83, which is used as 
the standard of compar- 
ison, will give a candle 
power determined from 
the height of the jet of 
the burning gas. This 
height is measured in 
millimetres by a mov- 
able circular screen. 

The determination of 
the candle power of 
gas by means of a jet photometer is only approximately cor- 
rect, unless many precautions are taken. 

Card, Compass A card used in a mariner's com- 
pass, on which are marked the points of the compass. (See 
Compass Card. Azimuth Compass.) 

Cascade, Charging Leyden Jars by — A 

device for charging jars or condensers by means of the free 
electricity liberated by induction in one coating, when a charge 
is passed into the other coating. 

The jars are placed as shown in Fig. 84, with the inside coat- 
ing of one jar connected with the outside coating of the one 
next it. There is in reality no increase in the entire charge 
obtained by the use of charging by cascade since the sum of the 




Fig. 82. 



Fig. SS. 



110 A DICTIONARY OF ELECTRICAL 

charges given to the separate jars is equal to the same charge 
given to a single jar separately charged. 

The energy of the discharge in cascade can be shown to be 
less than that of the same charge when confined to a single jar. 




Fig. Sh. 
i at liion. — A term sometimes used instead of Kation. 
More correctly written Kathion. (See Kathion.) 
Cathode. — A term sometimes used instead of Kathode. 
More correctly written Kathode. (See Kathode.) 
Caoutchouc, or India-rubber. — A resinous sub- 
stance obtained from the milky juices of certain tropical trees. 
Caoutchouc possesses high powers of electric insulation. 

Cautery, Electric or Galvano-Cautery. —In elec- 
tro therapeutics, the application of platinum wires of various 
shapes, heated to incandescence by the electric current, and 
used, in place of a knife, for removing diseased growths, or 
for stopping hemorrhages. 

The operation, though painful during application, is after- 
wards less painful than that with a knife, since secondary 
hemorrhage seldom occurs, and the wound rapidly heals. 

Galvano-cautery is applicable in cases where the knife would 
be inadmissible owing to the situation of the parts or their 
surroundings. 

Cell, Voltaic The combination of two metals, or 

of a metal and a metalloid, which when dipped into a liquid 
or liquids called electrolytes, and connected outside the liquid 
by a conductor, will produce a current of electricity. 



WORDS, TERMS AND PHRASES. Ill 

Different liquids or gases may take the place of the two 
metals, or of the metal and metalloid. (See Gas Battery.) 

Plates of zinc and copper dipped into a solution of sulphuric 
acid and water, and connected outside the liquid by a conduc- 
tor form a simple voltaic cell. 

If the zinc be of ordinary commercial purity, and is not con- 
nected outside the liquid by a conductor, the following- pheno- 
mena occur : 

(1) The sulphuric acid or hydrogen sulphate, H 2 S0 4 , is de- 
composed, zinc sulphate, ZnS0 4 , being formed, and hydro- 
gen, H 2 , liberated. 

(2) The hydrogen is liberated mainly at the surface of the 
zinc plate. 

(3) The entire mass of the liquid becomes heated. 

If, however, the plates are connected outside the liquid by 
a conductor of electricity, then the phenomena change and 
are as follows, viz. : 

(1) The sulphuric acid is decomposed as before, but 

(2) The hydrogen is liberated at the surface of the copper 
plate only. 

(3) The heat no longer appears in the liquid only, but also 
in all parts of the circuit, and 

(4) An electric current now flows through the entire cir- 
cuit, and will continue so to flow as long as there is any sul- 
phuric acid to be decomposed, or zinc with which to form 
zinc sulphate. 

The energy which previously appeared as heat only, noiv 
appears as electric energy. 

Therefore, although the mere contact of the two metals 
with the liquid will produce a difference of potential, it is the 
chemical potential energy, which become kinetic during the 
chemical combination, that supplies the energy required to 
maintain the electric current. (See Energy. Kinetic Po- 
tential. 

Simple Voltaic Cell. — A simple voltaic cell consists of two 



112 



A DICTIONARY OF ELECTRICAL 



plates of different metals, or of a metal and a metalloid (or 
of two gases, or two liquids, ot* of a liquid and a gas), each of 
which is called a voltaic element, and which, taken tog-ether, 
form what is called a voltaic couple. 

The voltaic couple dips into a liquid called an electrolyte, 
which, as it transmits the electric current, is decomposed by 
it. The elements are connected outside the electrolyte by any 
conducting- material. 

Direction of the Current. — In any voltaic cell the current is 
assumed to flow through the liquid, from the metal most 
acted on to the metal least acted on, and outside the liquid, 
through the outside circuit, from the metal least acted on to 
the metal most acted on. 

In Fig. 85, a zinc-copper voltaic couple 
is shown, immersed in dilute sulphuric 
acid. Here, since the zinc is dissolved 
by the sulphuric acid, the zinc is oosi- 
tive, and the copper negative in the li- 
quid. The zinc and copper are of oppo- 
site polarities out of the liquid. 

It will of course be understood that in 
the above sketch the current flows only 
on the completion of the circuit outside 
the cell, that is, when the conductors at- 
tached to the zinc and copper plates are electrically con- 
nected. 

Amalgamation of the Zinc Plate. — When zinc is used for 
the positive element, it will, unless chemically pure, be dis- 
solved by the electrolyte when the circuit is open, or will 
be irregularly dissolved while the circuit is closed, producing 
currents in little closed circuits from minute voltaic couples 
formed by the zinc and such impurities as carbon, lead, or iron, 
etc., always found in commercial zinc. (See, Action, Local.) 
As it is practically impossible to obtain chemically pure zinc, 
it is necessary to amalgamate the zinc plate, that is, to cover 




Fig. 85. 



WORDS, TERMS AND PHRASES. 113 

it with a thin layer of zinc amalgam. (See Zinc, Amalgama- 
tion of.) 

Polarization of the Negative Plate. — Since the evolved hy- 
drogen appears at the surface of the negative plate, after a 
while the surface of this plate, unless means are adopted to 
avoid it, will become coated with a film of hydrogen gas, or 
as it is technically called, will become polarized. (See Polari- 
zation of Voltaic Cell.) 

The effect of this polarization is to cause a falling off or 
weakening of the current produced by the battery, due to the 
formation of a counter-electro-motive force produced by the 
hydrogen-covered plate ; that is to say, the negative plate, 
now being covered with hydrogen, a very highly electro-posi- 
tive element, tends to produce a current in a direction opposed 
to that of the cell proper. (See Counter-Electro-Motive Force.) 

In the case of storage cells, this counter-electro-motive force 
is employed as the source of secondary currents. (See Storage 
of Electricity. Storage Cells.) 

In order to avoid the effects of polarization in voltaic cells, 
and thus ensure constancy of current, the bubbles of gas at the 
negative plate are mechanically carried off either by roughen- 
ing its surface, by forcing the electrolyte against the plate as by 
shaking, or by a stream of air ; or else the negative plate is 
surrounded by some liquid which will remove the hydrogen, 
by entering into combination with it. (See Polarization of 
Voltaic Cell.) 

Voltaic cells are therefore divided into cells with one or with 
two fluids, or electrolytes, or, into 

(1) Single-fluid cells, and 

(2) Double-fluid cells. 

Very many forms of voltaic cells have been devised. The 
following are among the more important, viz. : 
Single-Fluid Cells. 

The Grenet, Poggendorff, or Bichromate Cell. — A zinc-car- 
bon couple used with an electrolyte known as electropoion, a 



114 



A DICTIONARY OF ELECTRICAL 



solution of bichromate of potash and sulphuric acid in water. 
(See Electropoion Liquid.) 

The zinc, Fig. 86, is amalgamated and placed between two 
carbon plates. The terminals connected 
with the zinc and carbon are respect- 
ively negative and positive. In the 
form shown in the figure, the zinc plate 
can be lifted out of the liquid when the 
cell is not in action. 

The bichromate cell is excellent for pur- 
poses requiring strong currents, where 
long action is not necessary. As this cell 
readily polarizes, it cannot be advan- 
tageously employed for any considerable 
period of time. It becomes depolarized, 
however, when left for some time on 
open circuit. 

The following chemical reaction takes 
place when the cell is furnishing cur- 
Fig.86. rent, viz.: 

K 2 Cr 2 7 -f7H 3 S0 4 +3Zn=K 2 S0 4 +3ZnS0 4 +Cr 2 3(S0 4 )+7H 2 0. 
This cell gives an electro-motive force of about 1.987 volts. 
The Smee Cell— A zinc-silver couple used with an electro- 
lyte of dilute sulphuric acid, H 2 S0 4 . 

The silver plate is covered with a rough coating of metallic 
platinum, in the condition known as jjlatinum black. (See 
Platinum Black.) This cell was formerly extensively em- 
ployed in electro-metallurgy but it is now replaced by dyna- 
mo-electric machines. (See Electro-Metallurgy. Dynamo- 
Electric Machine.) 

A zinc-carbon couple is sometimes used to replace the zinc- 
silver couple. A couple of zinc-lead is also used, though not 
very advantageously. 

The Zinc-Copper Cell— A zinc-copper couple used with 
dilute sulphuric acid. 




WORDS, TERMS AND PHRASES. 



115 



This was one of the earliest forms of voltaic cells. 

In the zinc-silver, or the zinc-copper couple, the chemical 
reaction that takes place when the cell is furnishing' current 
is as follows, viz. : 

Zn + Ho S0 4 = Zn S0 4 + H 2 . 

The Smee cell gives an electro-motive force of about .65 volts. 
Double-Fluid Cells. 

Grove's Cell. — A zinc-platinum couple the elements of 
which are used with electrolytes of sulphuric and nitric acids 
respectively. 

The zinc, Z, Fig. 87, is 
amalgamated and placed 
into dilute sulphuric acid, 
and the platinum, P, into 
strong nitric acid (H N0 3 ), 
placed in a porous cell to 
separate it from the sul- 
phuric acid. (See Porous 
Cells.) In this cell the cur- 
rent is moderately constant, 
since the polarization of the 
platinum plate is prevented 
by the nitric acid that oxy- 
dizes and thus removes the 
hydrogen that tends to be 
liberated at its surface. The 
constancy of the current 
is not maintained for any 
considerable time, since the two liquids are rapidly decom- 
posed, or consumed, zinc sulphate forming- in the sulphuric 
acid, and water in the nitric acid. 

The chemical reactions are as follows, viz. : 
Zn + H 8 S0 4 =ZnS0 4 + H.; 
6H + 2H NO a = 4H + 2NO; 
2NO + 2 =N 2 4 . 




Fig. 87. 



116 



A DICTIONARY OF ELECTRICAL 




Fig. 88. 



This cell gives an electro-motive force of 1.93 volts. 
BunserCs Cell.— A. zinc-carbon couple, the elements of 
which are immersed respectively 
in electrolytes of dilute sulphuric 
and strong nitric acids. 

Bunsen's cell is the same as 
Grove's except that the platinum 
is replaced by carbon. The zinc 
surrounds the porous cell contain- 
ing the carbon. The polarity is 
as indicated in Fig. 88. 

The Bunsen cell gives an electro- 
motive force of about 1.96 volts. 

DanielVs Cell. — A zinc-copper 
couple, the elements of which 
are used with electrolytes of dilute 
sulphuric acid, and saturated so- 
lution of copper sulphate respectively. 

The copper element is made in the form of a cylinder c, 
Fig. 89, and is placed in a 
porous cell. The copper cyl- 
inder is provided with a wire 
basket near the top, filled 
with crystals of blue vitriol, 
so as to maintain the strength 
of the solution while the cell 
is in use. The zinc is in the 
shape of a cylinder and is 
placed so as to surround the 
porous cell. This cell gives a 
nearly constant electro-mo- 
tive force. 

The constancy of its action 
depends on the fact that for 
every molecule of sulphuric 
acid decomposed in the outer cell, an additional molecule 




WORDS, TERMS AND PHRASES. 



117 



of sulphuric acid is supplied by the decomposition of a mole- 
cule of copper sulphate in the inner cell. This will be better 
understood from the following- reactions which take place, viz. : 
Zn + H 2 S0 4 = Zn S0 4 + H 2 
Ho + Cu S0 4 — Ho S0 4 -f Cu. 
The H 3 S0 4 , thus formed in the inner cell, passes through 
the porous cell, and the copper is deposited on the surface of 
the copper plate. 

The Daniell's cell gives an electro-motive force of about 
1.072 volts. 

A serious objection to this form of cell arises from the fact 
that the copper is gradually deposited over the surface and in 
the pores of the porous cell, thus greatly varying its resistance. 
Callaud's Gravity Cell. — A zinc-copper couple, the ele- 
ments of which are em- 
ployed with electrolytes of 
dilute sulphuric acid, or di- 
lute zinc sulphate, and a con- 
centrated solution of cop- 
per sulphate respectively. 
This cell was devised in 
order to avoid the use of a 
porous cell. As its name in- 
dicates, the two fluids are 
separated from each other 
by gravity. 

The copper plate is the 
lower plate, and is surround- 
ed by crystals of copper sul- 
ig ' phate. The zinc, generally 

in the form of an open wheel, or crowfoot, is suspended near 
the top of the liquid, as shown in Fig. 90. 

The reactions are the same as in the Daniell cell. 
A dilute solution of zinc sulphate is generally used to replace 
the dilute sulphuric acid. It gives a somewhat lower electro- 
motive force, but ensures a greater constancy for the cell. 




118 



A DICTIONARY OF ELECTRICAL 




The Leclanche Cell. — A zinc-carbon couple the elements of 
which are used with a solution of sal-ammoniac, and a finely 
divided layer of black-oxide of manganese respectively. 

The zinc is in the form of a slender rod and dips into a sat- 
urated solution of sal-ammoniac, NH 4 CI. 

The negative element consists of a plate of carbon, C, Fig. 

91, placed in a 
r porous cell, in 
which is a mix- 
ture of black ox- 
ide of manganese 
and broken gas- 
retort c a r b o n , 
tightly packed 
around the c a r- 
b o n plate. By 
this means a greatly extended surface of carbon surrounded 
by black oxide of manganese, Mn 2 , is secured. The entire 
outer jar, and the spaces inside the porous cell are filled with 
the solution of sal-ammoniac. This cell, though containing 
but a single fluid, belongs, in reality, to the class of double- 
fluid cells, being one in which the negative element is sur- 
rounded by an oxidizable substance, the black oxide of man- 
ganese, which replaces the nitric acid, or copper sulphate in 
the preceding cell. 

The reactions are as follows, viz. : 

Zn+2(NH 4 Cl) = ZnCl 2 + 2NH 3 +H 2 . 
The Zn Cl 2 and NH 3 react as follows : 

Zn C1 2 + 2(NH 3 ) = (2NH 2 ) Zn Cl 2 +H 2 . 

2H + 2(Mn 2 2 ) = H 2 + Mn 2 3 , 

or, possibly, 4H + 3Mn 2 = Mn 3 4 -f- 2H 2 O. 

The Leclanche cell gives an electro-motive force of about 

1.47 volts. It rapidly polarizes, and cannot, therefore, give a 

steady current for any prolonged time. When left on open 

circuit, however, it rapidly depolarizes. 



WORDS, TERMS AND PHRASES. 



119 



Of all the voltaic cells that have been devised two only, 
viz., the Gravity and the Leclanche, have continued until 
now in very general use. The gravity cell being used on 
closed-circuit lines and the Leclanche on open-circuit lines ; 
the former being the best suited of all cells to furnish con- 
tinuous constant currents employed in most systems of tele- 
graphy, and the latter for furnishing the intermittent cur- 
rents required for ringing bells, operating annunciators, or for 
similar work. 

The Siemens- Halske Cell. — 
A zinc-copper couple the ele- 
ments of which are employed 
with dilute sulphuric acid and 
saturated solution of copper sul- 
phate respectively. 

This cell is a modification of 
Daniell's. A ring of zinc, Z Z, Fig. 
92, surrounds the glass cylinder 
c, c. The porous celJ is replaced 
by a diaphragm, / /, of porous 
paper, formed by the action of 
sulphuric acid on a mass of paper 
pulp. Crystals of copper-sulphate 
are placed in the glass jar, c c, ___ 
and rest on the copper plate A:, ~~ 
formed of a close copper spiral. 
Terminals are attached at b and 
h. The entire cell is charged with 
The resistance of the cell is high. 

The Meidinger Cell. — A zinc-copper couple the elements of 
which are employed with dilute sulphuric acid, or solution of 
sulphate of magnesia, and strong nitric acid, respectively. 

This is another modification of the Daniell cell. The zinc- 
copper couple is thus arranged : Z Z, Fig. 93, is an amalga- 
mated zinc ring placed near the walls of the vessel, A A. The 




Fig. 92. 
dilute sulphuric acid. 



120 



A DICTIONARY OF ELECTRICAL 




copper element c is similarly placed with respect to the ves- 
,4- sel b b. The glass cylinder h 
filled with crystals of copper sul- 
phate, has a small hole in its bot- 
tom, and keeps the vessel, b b, 
supplied with saturated solution 
of copper sulphate. The cell is 
charged with dilute sulphuric acid, 
or a dilute solution of Epsom 
salts, or magnesium sulphate. 
Cell, Standard Voltaic 

(See Standard Voltaic 

Cell) 

Cements, Insulating 

— Various mixtures of gums, resins 
and other substances, possessing 
the ability to bind two or more 
Fig. 93. substances together and yet to 

electrically insulate one from the other. 
Centi (as a prefix). — The one hundredth of. 
Centigrade Thermometer Scale. — A thermometer 
scale on which the freezing point of water is marked 0°, and 
the boiling point at 30 inches of the barometer 100°. 

Centigrade degrees are indicated by a C, thus 0° C. or 
100° C, to distinguish them from Fahrenheit degrees that are 
marked F. — (See Thermometer.) 

Centigramme. — The hundredth of a gramme, or 1544 
grains. (See Metric System of Weights and Measures.) 

Centimetre. — A length equal to the one hundreth of a 
metre or .3937 inch. (See Metric System of Weights and 
Measures.) 

Centimetre-Gramme-Second System, or the C. 
O. S. System. — A system of units of measurement in which 
the centimetre is adopted for the unit of the length, the 



WORDS, TERMS AND PHRASES. 121 

gramme for the unit of mass, and the second for the unit of 
time. 

This is the same as the Absolute System of Units. (See 
Absolute Units.) 

Central Station Lighting.— (See Lighting, Central 
Station. 

Centre of Oravity.— (See Gravity, Centre of.) 
Centre of Oscillation.— (See Oscillation, Centre of.) 
Centre of Peren§§ion.— (See Percussion, Centre of.) 
Centrifugal Force (so called).— The force that is sup- 
posed to urge a rotating body directly away from the centre 
of rotation. 

If a stone be tied to a string and whirled around, and the 
string break, the stone will not fly off directly away from the 
centre, but will move along the tangent to the point where it 
was when the string broke. 

The centrifugal force in reality is the force which is repre- 
sented by the tension to which the string is subjected during 
rotation. 

Centrifugal Governor A device for maintain- 
ing constant the speed of a steam engine or other prime 
mover, despite sudden changes in the load, or work. 

In a ball governor any increase in speed causes the balls to 
fly out from the centre of rotation by centrifugal force, which 
is utilized to control a valve or other regulating device. If 
the speed falls the balls move towards the centre, shifting the 
valve or regulating device in the opposite direction. 

Chain, Molecular (See Molecular Chain.) 

Chamber of Lamp.— The glass bulb or chamber of an 
incandescing electric lamp in which the incandescing con- 
ductor is placed, and which is generally maintained at a high 
vacuum. 

Characteristic Curves.— Diagrams in which curves are 
employed to represent the ratio of certain varying values. 



122 



A DICTIONARY OF ELECTRICAL 



The electro-motive force generated in the armature coils of 
a dynamo-electric machine, when the magnetic field is of a 
constant intensity, is theoretically proportional to the speed 
of rotation. (In practice this is prevented by a number of cir- 
cumstances). The relation existing between the speed and 
electro-motive force may be graphically represented by refer- 
ring the values to two straight lines, one horizontal and the 
other vertical, called respectively the 
axes of abscissas and ordinates. 
(See Abscissas, Axis of.) If, in a 
given case, the number of revolutions 
are marked off along the horizontal 
line from the point 0, Fig. 94, in dis- 
600 vm lances from 0, proportional to the 

Fig. 9h. number of revolutions, and the cor- 

responding electro-motive forces are marked off along the 
vertical line in distances from 0, proportional to the electro- 
motive forces, the points where these lines intersect, will 
form the characteristic curve as shown for the particular 
case. 




Charge, Bound and Free 

Free Charge.) 



— (See Bound and 



Charge, Density of 



or Electrical Density. 



The quantity of electricity at any point on a charged surface. 
Coulomb used the phrase Surface Density to mean the 
quantity of electricity per unit of area at any point on a 
surface. 



Charge, Electric 



-The quantity of electricity 



that exists on the surface of an insulated electrified conductor. 
When such a conductor is touched by a good conductor con- 
nected with the earth, it is discharged. 



Charge, Dissipation of - 

Charge.) 

Charge, Distribution of 



-(See Dissipation of 
— The variations that 



WORDS, TERMS AND PHRASES. 1*23 

exist in the density of an electrical charge at different portions 
of the surface of all insulated conductors except spheres. 

The density of charge varies at different points of the sur- 
face of conductors of various shapes. It is uniform at all 
points on the surface of a sphere. 

It is greatest at the extremities of the longer axis of an egg 
shaped body, and greater at the sharper end. 

It is five times greater at the corners of a cube than at the 
middle of a side. 

It is greatest round the edge of a circular disc. 

It is greatest at the apex of a cone. 

Charge, Residual The charge possessed by a 

charged Leyden jar a few moments after it has been dis- 
l-uptively discharged by the connection of its opposite coatings. 

The residual charge is probably due to a species of dielectric 
strain, or a strained position of the molecules of the glass 
caused by the charge. Such residual charge is not present in 
air condensers. 

Charge, Return (See Back Stroke or Return.) 

Charging' Aeeuuiulators. — Sending an electric current 
into a storage battery for the purpose of rendering it an elec- 
tric source. 

There is, strictly speaking, no accumulation of electricity 
in a storage battery, such for example as takes place in a 
condenser. (See Storage Batteries). 

Charaeteristies of Sound.— The peculiarities that 
enable different musical sounds to be distinguished from one 
another. 

The characteristics of musical sounds are : 

(1) The Tone or Pitch, according t which a sound is either 
grave or shrill. 

(2) The Intensity or Loudness, according to which a sound 
is either loud or feeble. 

(3) The Quality or Timbre, the peculiarity which enables us 



124 



A DICTIONARY OF ELECTRICAL 



to distinguish between two sounds of the same pitch and 
intensity, but sounded on different instruments, as for example 
on a flute and on a piano. 

Chemical Effect or Change. — Such a change, occa- 
sioned by chemical combination, as results in a loss of thoce 
properties or peculiarities by which the substances entering 
into combination are ordinarily recognized. 

Black carbon, and yellow sulphur, for example, both solids, 
unite chemi . ; Ay to form a transparent colorless liquid. 

Chemical changes differ from physical changes, which latter 
can occur in a substance without the loss by it of the proper- 
ties it ordinarily possesses. 

Thus a sheet of vulcanite, electrified by friction, still retains 
its characteristic density, shape, color, etc. 

Chemical Equivalent. — (See Equivalent, Chemical.) 

Chemical Photometer. — (See Photometers.) 

Chemical Potential Energy. — (See Energy Atomic, 
or Energy Potential.) 

Chemical Recorder. — (See Recorder, Chemical, Bain's.) 




Chimes, Electric 



-Bells, 
repul- 



Fig. 95. 



rung by the attractions and 
sions of electrostatic charges. 

B and B, Fig. 95, are directly con- 
nected to the prime or positive 
conductor -f-j of a frictional machine. 
C is insulated from this conductor 
by means of a silk thread, but is con- 
nected with the ground by the me- 
tallic chain C. Under these circum- 
stances the clappers, I I, insulated 
by silk threads, t t, are attracted 
to B, B, by an induced charge and 



repelled to C, where they lose their charge only to be again 



WORDS, TERMS AND PHRASES. 



125 



attracted to B, B. In this way the bells will continue ringing 
as long as the electric machine is in operation. 

Chronograph, Electric — An apparatus for 

electrically measuring and registering small intervals of time. 

Chronographs, though of a variety of forms, generally regis- 
ter minute intervals of time by causing a tuning fork or vibrat- 
ing bar of steel, whose rate of motion is accurately known, to 
trace a sinuous line on a smoke blackened sheet of paper, 
placed on a cylinder driven by clockwork, at a uniform rate 
of motion. If a fork that is known to produce, say, 256 vibra- 
tions per second be used, each sinuous line will represent ? |g 
part of a second. 

An electro-magnet is used to make marks on the line at the 
beginning and the end of the observation, and thus permit its 
duration to be measured. 

An apparatus for elec- 



Chrono§cope, Electric 

trically indicating, but not necessarily recording, small inter- 
vals of time. 

The small interval of time required for a rifle ball to pass 
between two points may be determined by causing the ball to 
pierce two wire screens placed a known distance apart. As 
the screens are successively pierced, an electric circuit is thus 
made or broken, and marks are registered electrically on any 
apparatus moving with a known velocity. 

Circle, Azimuth —(See ^ 

Azimuth Circle.) ^ 



Circle, Voltaic or Galvanic 

A name formerly employed t 



for a voltaic cell or circuit. 
Circuit, Astatic 



A cir- | 



+ s 



cuit consisting of two closed curves "' |b 

enclosing equal surfaces. Fig. 96. 

Such a circuit is not under the action of the earth's field. 
The circuit disposed ? as shown in Fig. 96, is astatic and pro- 



126 A DICTIONARY OF ELECTRICAL 

duces two equal and opposite fields at S and S'. (See Mag- 
netism, Ampere's Theory of.) 

Circuit, Broken or Opened, Made, Closed, or 

Completed A circuit is broken or opened, when its 

conducting continuity is disturbed, or when the current can- 
not pass. 

Circuit, Closed, Completed or Made A 

circuit is closed, completed, or made when its conducting 
continuity is such that the current can pass. 

Circuit, Compound A circuit containing more 

than a single source, or more than a single electro-receptive 
device, or both, connected by conducting wires. 

The term compound circuit is sometimes applied to a series 
circuit. (See Circuit, Series.) The term, however, is a bad 
one, and is not generally adopted. 

Circuit, Earth' A circuit in which the ground 

or earth forms part of the conducting path. (See Circuit, 
Varieties of.) 

Circuit, Electric Literally to go around. 

The path in which electricity circidates or passes from a 
given point, around or through a conducting path, back again 
to its starting point. 

All simple circuits consist of the following parts, viz. : 

(1) Of an electric Source, which may be a voltaic battery 
a thermo-pile, a dynamo-electric machine, or any other means 
for producing electricity. 

(2) Of Leads or Conductors for carrying the electricity out 
from the source, through whatever apparatus is placed in the 
line, and back again to the source. 

(3) Various Electro-Receptive Devices, such as electro-mag- 
nets, electrolytic baths, electric motors, electric heaters, etc., 
through which the current passes and by which they are ac- 
tuated or operated, 



WORDS, TERMS AND PHRASES. 



127 



Circuit, External 



external, or outside the electric 
Circuit, Grounded 



-That part of a circuit which is 
source. 

A circuit in which the 

through which the current 

good conductor, the terminals 
gas or water pipes, or with 
plates. Such connection, or 
is usually termed the ground 



ground forms part of the path 
passes. 

As the ground is not always a 
should be connected with the 
metallic plates, called ground 
any similar ground connection 
or earth. 

Circuit Indicator.— (See Indicator.) 

Circuit, Internal ■ — That part of a circuit which is 

included within the electric source. 

Circuit, Line The wire or other conductors in 

the main line of any telegraphic or other electric circuit. (See 
Circuits, Varieties of.) 

Circuit, Local ■ —The circuit in a telegraphic system 

in which is placed a local battery as distinguished from a main 
battery. (See Telegraph, Morse System.) 

Circuit, Main Battery -A term sometimes used 

for Line Circuit. (See Circuit, Line.) 

Circuit, Magnetic —The path through which the 

lines of magnetic force 
pass. 

All lines of force form 
closed circuits. 

In the bar magnet, 
shown in Fig. 97, part of 
this path is through the 
air. In order to reduce 
or lower the resistance Fig. 97 

of a magnetic circuit, iron is often placed around the mag- 
net. The magnet is then said to be iron-clad. 

The armature of a magnet lowers the masrnetic resistance 




128 A DICTIONARY OF ELECTRICAL 

oy affording a better path for the lines of magnetic force than 
the air between the poles. 

Circuit, Metallic A circuit in which the ground 

is not employed as any part of the path of the current. 

Circuit, multiple-Series ——(See Circuits, Varie- 
ties of.) 

Circuit, Parallel or Multiple-Arc (See Cir- 
cuits, Varieties of.) 

Circuit, Simple A circuit containing a single 

electric source, and a single electro-receptive device, connected 
by a single conductor. 

The term simple circuit is sometimes applied to a multiple 
arc circuit. The term is not, however, a good one, and is not 
in general use. 

Circuit, Series (See Circuits, Varieties of.) 

Circuit, Series-Multiple (See Circuits, Varie- 
ties of.) 

Circuit, Shunt or Derived A circuit which 

forms an additional path for an electric current. (See Shunt, 
or Derived Circuit.) 

Circuits, Varieties of Conducting paths pro- 
vided for the passage of an electric current. 

Electric circuits may be divided according to their complex- 
ity into 

(1) Simple. 

(2) Compound. 

According to the peculiarities of their connections into 

(1) Shunt or Derived. 

(2) Series. 

(3) Parallel or Multiple- Arc, 

(4) Multiple-Series. 

(5) Series-Multiple. 



WORDS, TERMS AND PHRASES, 129 

According to their resistance into 

(1) High Resistance. 

(2) Low Resistance. 

According to their relation to the electric source into 

(1) Internal circuits. 

(2) External circuits. 

According to their position in the circuit, or the work 
done, circuits are divided into very numerous classes; thus in 
telegraphy we have the following, viz. : 

(1) The Line circuit. 

(2) The Earth or Ground circuit. 

(3) The Local Battery circuit. 

(4) The Main Battery circuit, etc. 

A simple circuit is one which contains but a single electric 
source and a single electro-receptive device, connected by a 
single conducting wire. 

A compound circuit is one which contains more than a 
single electric source, or more than a single electro-receptive 
device, or both, connected by conducting wires. 

Either the circuits, the sources, or the electro-receptive de- 
vices ma} r be connected in series, in multiple, in multiple-series, 
or in series-multiple. 

The most important of these are as follows : 

(1) Series circuits or connections. Compound circuits, in 
which the separate circuits, or sources, are connected in one 
line by joining their opposite poles so that the current pro- 
duced in each passes successively through the circuit. 




Fig. 98. 



The six cells, shown in Fig. 98, are connected in series 
by joining the positive pole of each cell with the negative 



130 



A DICTIONARY OF ELECTRICAL 




pole of the succeeding cell, the negative and positive poles at 
the extreme ends being connected by any conductor. 

The connection 
of three Leclan- 
cle cells in series 
is clearly shown 
in Fig. 99. The 
carbons, C C, of 
the first and sec- 
ond cells are con- 
Fig.99. nected to the 

zincs, Zn Zn, of the second and third cells, thus leaving the 
zinc, Zn, of the first cell, and the carbon, C, of the third cell, 
as the terminals of the battery. The direction of the current 
is shown by the arrows. 

The resistance of such a connection is equal to the sum of 
the resistances of each of the separate sources. 

The electro-motive force is equal to the sum of the separate 
electro-motive forces. 

If the electro-motive force of a single cell is equal to E, its 
internal resistance to r, and the resistance of the leads and 
electro-receptive devices to r', then the current in the circuit, 



E 



C = 



r -\-r' 

If six of such cells are coupled in series, the current becomes 

6E 
C= . 



6r -j-r 
If, however, the internal resistance of each cell be so small 
as to be neglected, the formula becomes 

6E 

a •* — ; 



or the current is six times as great as with one cell. 



WORDS, TERMS AND RHRASES. 



181 



The series connection of battery cells is used on telegraph 
linen, or in all cases where a high electro-motive force is re- 
quired in order to overcome a considerable resistance in the 
circuit. The instruments are also generally connected to the 
line in series. 

This series connection was formerly called Connection for 
Intensity. The term is now abandoned. 

C ^ A C 




Fig. 100. 

(2) Parallel Circuit, or Multiple-Arc. — A compound circuit 
in which the separate sources, or the separate electro-receptive 
devices, or both, are connected by one set of terminals, such 
as the positive, to one lead, or main positive conductor ; and 
all the negative terminals are similarly connected to another 
lead, or main negative conductor, as shown in Fig. 100. 




Fig. 101. 
The connection of three Bunsen cells, in multiple-arc, is 
shown in Fig. 101, where the three carbons, C C C, are con- 



132 



A DICTIONARY OF ELECTRICAL 



nected together to form the positive, or -f- terminal of the 
battery, aud the three zincs, Zn Zn Zn, are similarly connected 
together to form the negative, or — terminal. 

The electro-motive force is the same as that of a single cell, 
or source. The internal resistance of the source is as much 
less than the resistance of any single source as the area of 
the combined negative or positive plates is greater than that 
of any single negative or positive plate ; or, in other words, is 
less in proportion to the number of cells, or other separate 
sources so coupled. 

In the case of the six cells above referred to, the current 
would be, 

E 



C = r 

-+r> 

6 
where E, is the electro-motive force, r, the internal and r\ 
the external resistance. 

The effect of multiple connection on the internal resistance 
of the source is to increase the area ol cross section of the 
liquid in the direct proportion of the number of cells added. 

C 





1 



Fig. 102. 

"When strong or large currents of low electro-motive force are 
required, connections in multiple-arc are generally employed. 

The multiple-arc connection was formerly called the Con- 
nection for Quantity. This term is now abandoned. 



WORDS, TERMS AND PHRASES. 



133 




(3) Multiple-Series Circuit.— A compound circuit in which 
the separate sources, or electro-receptive devices, are con- 
nected in groups in multiple- arc, and the members of each 
group subsequently connected in series. 

In Figs. 102 and 103, multiple-series circuits of six sources 
are shown. The "— 
current takes the 
paths indicated ^f. 

by the arrows. 
The electro-mo- 
tive force of the 
source will be in- 
creased in pro- 
portion to the Fig. 103. 

number of cells in series, and the internal resistance decreased 
in proportion to the number in parallel. Supposing the circuit 
closed by a resistance equal to r', the current would be, in 
Fig. 102, 

2E 



and that in the Fig. 103, 



J 



1 


2r 




+ r' 

3 




3E 


c = 


= 3r 




+*' 



(4) In Series- Multiple; the method adopted in the use of dis- 
tribution boxes, a number of multiple groups or circuits are 



=* 1 * } * 

=^^~ — — r~ — =t 

* 4= * 

* *_ * 



Fig. 10k. 
connected with each other, in series, as shown in Fig. 104. 
(See Box, Distribution, for Arc Light Circuits.) 



134 A DICTIONARY OF ELECTRICAL 

In this connection the resistance of each multiple group is 
equal to the resistance of a single branch divided by the num- 
ber of branches. 

The total resistance of the circuit is equal to the sum of the 
resistances of the multiple groups. 

The resistances of the separate compound circuits is as fol- 
lows : Calling E', R", and R'", the resistance of each of the 
separate parts and the joint resistance R. 

(1) For the series circuit, 

R = R' _|_ R" _j_ R'". 

(2) For the parallel circuit, 

R= R'XR"XR"' 

R' R" -f R" R'" -f R' R'" ; 
or, what is the same thing, the conductivity of a multiple cir- 
cuit is the sum of the reciprocals of the separate resistances; 
1 1 1 

or, Conductivity = 1 1 . 

R' R" R'" 

(3) For the multiple-series circuit, if the resistance of each 
circuit is r, then the total resistance 

2r 
R= - , 
3 
when three are in parallel and two in series ; and 

dr 
R= - , 
2 
when two are in parallel and three in series. 

(4) For the series-multiple circuit, calling r the resistance 
of each separate circuit in the five parallel circuits, then 
the resistance of each of the parallel groups is 

r 
R= -; 
5 
and the total resistance of the three groups is 
r r r 3r 

R=-+- + - = -. 
5 5 5 5 



WORDS, TERMS AND PHRASES. -$5 

Circular Units. — Units based upon the value of the area 
of a circle whose diameter is unity. 
Circular Units (Cross-Sections), Table of. 

1 circular mil. _ = .78540 square mil. 

" = .00064514 circular millimetre. 

= .00050669 square millimetre. 

1 square mil = 1.2732 circular mils. 

_ = .00082141 circular millimetre. 

1 circular millimetre = 1550.1 circular mils. 

" = 1217.4 square mils. 

" = . 78540 square millimetre. 

1 square millimetre = 1973.6 circular mils. 

" -. = 1.2732 circular millimetres. 

If d is the diameter of a circle, the area in other units is ■ 
If d is in mils., area in sq. 

millimetres _ . . = d 2 x .00050669. 

d in millimetres, area in sq. 

mils = d 2 x 1217.4. 

d in centimetres, area in sq. 

inches = d 2 x 12174. 

d in inches, area in sq. centi- 
metres = d 2 x 5.0669. 

(Hering.) 
Clamp or Clutch for Arc Uamps.— A clamp for 
gripping the lamp-rod, i. e., the rod that supports the carbon 
electrodes of arc lamps. (See Lamp, Electric Arc.) 

Cleats. — Insulating supports for attaching wires to the 
walls or ceilings of buildings. 

Clepsydra, Electric An instrument for measur- 
ing time by the escape of water or other liquid under electrical 
control. 

Clocks, Electric Clocks, the works of which are 

moved either entirely or partially by the electric current, 
are controlled or regulated by the electric current, or «,re 
wound thereby. 



136 



A DICTIONARY OF ELECTRICAL 



Electric clocks may therefore be divided into three classes, 



(1) Those in which the works are moved entirely or partially 
by the electric current. 

(2) Those which are controlled or regulated by the electric 
current. 

(3) Those which are merely wound by the current. 

A clock moving- independently of electric power, is given a 
slight retardation or acceleration electrically and is thus pre- 
vented from gaining or losing time. The entire motion of 
the balance wheel is sometimes imparted by electricity. 

An example of one of many forms of electric clock is shown 
in Fig. 105, where the split battery (See Battery, S})lit), P N, is 
connected, as shown, to the spring contacts S and S'. 





Fig. 105. 

By these means currents are sent into the circuit in alter- 
nately opposite directions. The pendulum bob, Fig. 106, of the 
controlled clock is formed of a hollow coil of insulated wire, 
which encircles one or both of two permanent magnets, 



WORDS, TERMS AND PHRASES. 



137 



A and A', placed with their opposite poles feicing each other. 
In this manner a slight motion forwards or backwards is im- 
parted to the pendulum which is thus kept in time with the 
controlling- clock. 

The controlling clock is shown in Fig. 105, and the controlled 
clock in Fig. 106. Mercury contacts are sometimes employed 
in place of the springs S and S'. Induction currents may also 
be employed. 

Clocks of non-electric action may be electrically controlled, 
or correctly set at certain intervals, either automatically by a 
central clock, or by the depression of a key operated by hand 
from an astronomical observatory. 

In a system of Time Telegraphy, the controlling clock is 
called the Master Clock, and the controlled clocks the Second- 
ary Clocks. 

Secondary clocks are generally mere dials, containing step- 
by-stcp movements, for moving the hour, minute and second 
hands. (See Telegraphy, Stcp-by-Step.) 





Fig. 107. 

In Spellier\s clock, a series of armatures H, Fig. 107, 
mounted on the circumference of a wheel, connected with the 



138 A DICTIONARY OF ELECTRICAL 

escapement wheel, pass successively, with a step-by-step move- 
ment, over the poles of electro-magnets. On the completion 
of the circuit, they are attracted towards the magnet, and on 
the breaking of the circuit they are drawn away by the fall of 
the weight F, placed on the lever D, pivoted at E. A pulley 
at E, runs over the surface of a peculiarly shaped cog on the 
escapement wheel. 

Clock, Electric Annunciator A clock, the 

hands or works of which, at certain predetermined times, 
make electric contacts and thus ring bells, release drops, trace 
records, etc. 

Clock, Master The controlling clock used in a 

s3 T stem of time telegraphy. (See Clocks, Electric.) 

Clock-work Feed for Arc Lamps- Arrangements 
of clock-work for obtaining a uniform feed motion of one or 
both electrodes of an arc lamp. 

The clock-work is automatically thrown into or out of action 
by an electro-magnet, usually placed in a shunt circuit around 
the carbons. 

Clocks, Secondary The clocks in a system of 

time telegraphy that are controlled by the master clock. 
(See Clocks, Electric.) 

Clocks, Self- Winding Clocks that at regular 

intervals are automatically wound by the action of a small 
electro-magnetic motor contained in the clock. 

Closed Circuit,— (See Circuit, Closed, Completed or 
Made.) 

Closure. — The completion of an electric circuit. 

Coatings, Condenser The sheets of tin foil on 

opposite sides of a Leyden Jar or condenser, which receive the 
opposite charges. 

Coatings, Metallic Coverings or coatings of 

metals, deposited from solutions of metallic salts by the action 
of an electric current. (See Electro-Plating.) 



WORDS, TERMS AND PHRASES. 139 

Code, Cipher A code in which a number of words 

or phrases are represented by single words. 

The message thus received requires the possession of the 
key to render it intelligible. 

Code, Telegraphic The pre-arranged signals of 

any system of telegraphy. (See Alphabet, Telegraphic ; Morse, 
Continental.) 

Coefficient, Algebraic A number prefixed to 

any quantity to indicate how many times that quantity is to 
be taken. 

The number 3, in the expression 3a, is a coefficient and in- 
dicates that the a, is to be taken three times, as a -f- a -\- a = 3a. 

Coefficient, Economic of a Dynamo 

Electric Machine. — The ratio between the electrical en- 
ergy or the electrical horse power developed by the current 
produced by a dynamo, and the mechanical horse power ex- 
pended in driving the dynamo. 

The Efficiency may be the Commercial Efficiency, which is 
the useful or available energy in the external circuit divided 
by the total mechanical energy ; or it may be the Electrical 
Efficiency, which is the available electrical energy divided by 
the total electrical energy. 

The, Efficiency of Conversion in the total electrical energy 
developed, divided by the total mechanical energy applied. 

If M, equals the mechanical energy, 

\V, the useful or available electrical energy, and 
w, the electrical energy absorbed by the machine, and 
m, the Stray Power, or the power lost in friction, eddy 
currents, air friction, etc. Then, since 

M = W-|-!P-(- m, 

W W 



Commercial Efficiency . . 

Electrical Efficiency 

Efficiency of Conversion 



M W+w + ib 
W 



W-fw _ W-fw 



M W-fw-fm 



140 A DICTIONARY OF ELECTRICAL 

Coefficient, Economic (See Economic Coeffi- 
cient.) 

Coefficient of magnetization, or Coefficient of 
Magnetic Induction. — A number representing- the inten- 
sity of magnetization produced in a magnetizable body as 
compared with the intensity of magnetization of the induc- 
ing body. 

A magnetizable body, when placed in a magnetic field, con- 
centrates the lines of magnetic force on it, or causes them to 
run through it. The intensity of the magnetization so pro- 
duced depends, therefore, 

(1) On the intensity of the magnetizing field. 

(2) On the ability of the metal to concentrate the lines of 
force on it, that is, on the nature of the metal, or, on its mag- 
netic permeability. (See Magnetic Permeability.) 

The intensity of magnetization will therefore be equal to 
the product of the coefficient of magnetization, and the in- 
tensity of the magnetizing field. 

The coefficient of magnetization of paramagnetic bodies is 
said to be positive ; that of diamagnetic bodies to be negative 
because the former concentrate the lines of magnetic force on 
them, and the latter appear to repel them. (See Paramag- 
netic. Diamagnetic.) 

Coefficient of Mutual Induction.— A quantity rep- 
resenting the relative number of lines of magnetic force 
which each of two neighboring electric circuits induce in the 
other. 

Coefficients of Expansion. — The fractional increase 
in its dimensions of a bar or rod when heated from 32° to 
33° F., or from 0° to 1° C. 

The fractional increase in its length is called the Coefficient 
of Linear Expansion. 

The fractional increase in its surface is called the Coefficient 
of Surface Expansion, 



WORDS, TERMS AND PHRASES. 141 

The fractional increase in its volume is called the Coeffi- 
cient of Cubic Expansion. 
Coefficients of Linear Expansion. — 

Gold 0.000015153 

Steel 0.000010972 

Silver 0.000019086 

Copper 0.000017173 

Brass 0.000018782 

Tin 0.000019376 

Iron 0.000012350 

Flint glass 0.000008116 

Platinum 0.000009918 

Lead 0.000088483 

Zinc 0.000029416 

{Laplace and Lavoisier). 
Coercive, or Coercitivc Force. — The power of resist- 
ing magnetization or demagnetization. 

Coercive Force is sometimes called Magnetic Retentivity. 
Hardened steel possesses great coercive force ; that is, it is 
magnetized or demagnetized with difficulty. 
Soft iron possesses very feeble coercive force. 
It is on account of the feeble coercive force of the soft iron 
core of an electro-magnet that its main value depends, since 
it is thereby enabled to rapidly acquire its magnetization, on 
the completion of a battery circuit through its coils, and to 
rapidly lose its magnetization, on the opening of the circuit. 

Coils, Armature (See Dynamo-Electric Ma- 
chines, Armature Coils.) 

Coils, Electric Convolutions of insulated wire 

through which an electric current may be passed. (See Elec- 
tro-Magnet. 

Coils, Henry's A number of separate induction 

coils so connected that the currents induced in the secondary 
wire of the first coil are caused to induce currents in the 



142 



A DICTIONARY OF ELECTRICAL 



secondary wire of the second coil, with whose primary it is 
connected in series. 

A series of three of Henry's coils is shown in Fig. 108. 
An intermittent battery current is sent into a, the secondary 
of which, b, is connected with the primary c, of the second 
coil. The secondary d, of the second coil, is connected with 
the primary e, of the third coil, and the currents finally in- 
duced in /, are employed for any useful purpose, such as the 
magnetization of a bar of iron at g. 




Fig. 108. 




Fig. 109. 

The current in b is sometimes called a Secondary Current; 
that induced by this secondary current in d is called a Ter- 
tiary Current, or a Current of the Third Order; that in/, a 
Current of the Fourth Order. Henry carried these successive 
inductions up to currents of the Seventh Order. 

Henry's coils in reality consist of separate induction coils, 
connected, as above explained, in series. 

In Fig. 109, the tertiary current induced in IV., may be 
employed to give shocks to a person grasping the handles, 
e and/. 



WORDS, TERMS AND PHRASES. 



143 



Coils, Induction 



(See Induction Coils.) 




Coils, Magnet (See Magnet Coils.) 

Coils, Resistance Coils of wire, the electrical 

resistance of which is known, employed for measuring- the re- 
sistance of any circuit. 

In order to avoid the mag- 
netizing effects of the coils on 
the needles of the galvanome- 
ters used in electric measure- 
ments, the wire of the re- 
sistance coil is doubled on 
itself before being wound, 
and its ends electrically con- 
nected with the brass bars, . 
E, E, Fig. 110. The insertion 
of the plug-key cuts the coil 
out of the circuit by short- Fig. 110. 

circuiting. (See Box, Resistance. Balance, W heat stone' s> 
Electric. Standard Resistance Coil.) 

The coils are made of German silver, or platinoid, whose 
resistance is not much affected by heat. 

Coil*, Shu ill Coils placed in a derived or shunt 

circuit. (See Circuit, Shunt.) 

Collectors of Dynamo Electric Machines.— The 
metallic brushes that rest on the commutator cylinder, and 
carry off the current generated on the rotation of the arma- 
ture. Collectors are familiarly called commutators. 

Collectors, Electric. — Devices employed to collect or 
take off electricity from a moving electric source. 

Collectors of Frictional Electric Machines.— 

The metallic points that collect the charge from the glass plate 
or cylinder of a frictional electric machine. 

Column, Electric A term formerly applied to a 

voltaic pile. (See Pile, Voltaic.) 



144 A DICTIONARY OF ELECTRICAL 

Completed Circuit.— (See Circuit, Closed, Completed or 
Made.) 

Commercial Efficiency of Dynamo.— The useful or 
available electrical energy in the external circuit, divided by 
the total mechanical energy required to drive the dynamo 
that produced it. (See Coefficient, Economic, of Dynamo.) 

Commutator. — Generally, a device for changing the di- 
rection of an electric current. 

That part of a dynamo-electric machine that causes the cur- 
rents that alternate or change their direction twice in every 
revolution of the armature, between a pair of magnet poles, 
to flow in one and the same direction in the external circuit. 

One end of an armature coil is connected 
with A', Fig. Ill, and the other with A. 
The brushes are so set that A and A' are 
in contact with B' and B, respectively, as 
long as the current flows in the same 
direction, in the armature coil connected 
therewith, but enter into contact with. B 
and B', when the current changes its di- 
rection, and continue in such conjtact as 
as it flow T s in this direction. The current will therefore 
flow through any circuit connected with the brushes in one 
and the same constant direction. 

The number of metallic pieces A and A', in the commutator 
cylinder depends on the number, arrangement and con- 
nection of the armature coils, and on the disposition of the 
magnetic field of the machine. 

For details of various commutators of this description, see 
Dynamo-Electric Machines. 

The Reverscr used by Kuhmkorff in his induction coil, for 

cutting off, or for reversing the direction of the primary current 

is shown in Fig. 112, and was called by him the commutator. 

(See Ruhmkorff Coil.) 

Two metallic strips, V V, supported on a cylinder of insu- 




WORDS, TERMS AND PHRASES. 



145 



lating material are in contact with the battery terminals P 
and N through two vertical springs that bear on them. On a 
half rotation of the cylinder by the thumb screw L, the strips 
V, V, change places as regards the vertical springs, and thus 
reverse the direction of the battery current. 




Fig. 112. 



Compass, Azimuth, or Mariner's- 



-A compass 



used by mariners for measuring the horizontal distance of the 
sun or stars from the magnetic meridian. (See Azimuth, 
Magnetic.) 

A single magnetic needle, or several magnetic needles, are 
placed side by side on the lower surface of a card, called the 
compass card. This card is divided into the four cardinal 
points, N, S, E and W, and these again sub-divided in thirty- 
two points called Rhumbs. 

In the azimuth compass these divisions are supplemented 
by a further division into degrees. 



146 



A DICTIONARY OF ELECTRICAL 



A form of azimuth compass is shown in Fig. 113. In order 
to maintain the compass box in a horizontal position, despite 
the rolling of the ship, the box, A B, is suspended in 
the larger box, P Q, on two concentric metallic circles, C D, 

and E F, pivoted on 
two horizontal axes 
at right angles to 
each other ; or, as it 
is technically term- 
ed, in Gimbals. 
Sights, G H, are 
provided for meas- 
uring the magnetic 
azimuth of any ob- 
ject. 

Compass Card. 

— (See Compass, Az- 
imuth.) 

Compensating Magnet.— (See Magnet, Compensating.) 

Component, Horizontal and Ver- 
tical, of Earth's Magnetism.— That 

portion of the earth's directive force which 
acts in a horizontal direction. 

Let A B, Fig. 114,. represent the direction 
and magnitude of the earth's magnetic field 
on a magnetic needle. The magnetic force 
will lie in the plane of the magnetic meridian, 
which will be assumed to be the plane of the 
paper CAD. The earth's field, A B, can be 
resolved into two components, A D, the hori- 
zontal component, and A C, the vertical 
component. 

In the case of a magnetic needle, which, like the ordinary 
compass needle, is free to move in a horizontal plane only, the. 





Fig. Ilk. 



WORDS, TERMS AND PHRASES. 



147 



horizontal component alone directs the needle. When the 
needle is free to move in a vertical plane, and the plane cor 
responds with that of the magnetic meridian, this entire mag- 
netic force, A B, acts to place the needle, supposed to be 
properly balanced, in the direction of the lines of force of the 
earth's magnetic field at that point. In the vertical plane at 
right angles to the plane of the magnetic meridian, the ver- 
tical component alone acts, and the needle points vertical ly 
downwards. 

Components. — The two or more separate forces into 
which any single force may be resolved ; or, conversely, the 
separate forces which together produce any single resulting 
force. 

When two or more forces simultaneously act to produce 
motion in a bod}*, the bod}* will move with a given force in a 
single direction called the resultant. The separate forces, or 
directions of motion, are called the componods. 

Two forces acting simultaneously on a body at A, Fig. 115, 
tending to move it in the direction of the arrows, along A B 
and A C, with intensi- 
ties proportioned to the 
lengths of the lines A B 
and A C, respectively, 
will move it in the direc- 
tion A D, obtained by 
drawing B D and D C, 
parallel to A C and A B, 
respectively, and draw- 
ing A D through the point of intersection, D. This is called 
the Composition of Forces. A D is the resultant force and 
A B and A C are its components. 

Conversely, a single force, acting in the direction of D B, 
Fig. 116, against a surface, B C, may be regarded as the 
resultant of the two separate forces, D E and D C, one parallel 
to C B, and one perpendicular to it. D E, being parallel to 




Fig. in 



148 



A DICTIONARY OF ELECTRICAL 




C B, produces no pressure, and the absolute effect of the force 

B E will De represented by 

- CD. 

This is called the reso- 
lution of forces, the force, 
D B, being- resolved into 
the components D E and 
DC. 

That component of the 
Fig. 116. earth's magnetic force 

which acts in a horizontal,or in a vertical direction respectively. 
Compound, Binary Compound, Chatter- 
ton's. — A compound for cementing together the alternate 
coatings of gutta-percha employed on a cable conductor, or 
for filling up the spaces between the strand conductors. (See 
Binary Compound.) 

The composition is as follows : 

Stockholm tar 1 part by weight. 

Resin 1 " 

Gutta-percha 3 " 

(Clark & Sabine.) 

Compound, Clark's. — A compound for the outer casing 
of the sheath of submarine cables. 
Its composition is as follows : 

Mineral pitch 65 parts by weight. 

Silica 30 " 

Tar 5 

(Clark & Sabine.) 

Compound Magnet.— (See Magnet, Compound.) 

Compound Winding of Dynamo-Electric Ma- 
chines. — A method of winding in which shunt and series 
coils are placed on the field magnets. (See Dynamo-Electric 
Machines.) 



WORDS, TERMS AND PHRASES. 



149 



Concentric Carbon Electrodes,— (See Carbons, 
Cored.) 

Condenser, or Accumulator.— A device for increasing- 
the capacity of an insulated conductor by bringing it near 
another insulated earth-connected conductor, but separated 
from it by a medium that will readily permit induction to 
take place through its mass. 

If the conductor A, Fig. 117, standing alone and separated 
from other conductors, be connected with an electric machine, 
it will receive only a very small charge. 




Fig. W. 

If, however, it be placed near C, but separated from it by a 
dielectric, such as a plate of glass B, and C be connected with 
the ground, A will receive a much greater charge. (See Die- 
lectric.) 

Suppose, for example, that A be connected with the posi- 
tive conductor of a frictional electric machine ; it will by 
induction produce a negative charge to the surface of C, 
nearest it, and repel a positive charge to the earth. The 
presence of these two opposite charges on the opposed surfaces 
of A and C produces a neutralization that permits A to 
receive a fresh charge from the machine. (See Induction, 
Electrostatic.) 

The charge in a condenser in reality resides on the opposite 



150 



A DICTIONARY OF ELECTRICAL 







b 




; a 


A 




b 


a 








b S 




a 


\ 



surfaces of the glass, or other dielectric separating the metallic 
coatings, as can be shown by removing the coatings after 
charging. 

The condenser resulted from the discovery of the Leyden 
jar. (See Jar, Leyden.) 

The capacity of a condenser is meas- 
ured in microfarads (See Farad.) 

In practice condensers are made of sheets 
of tin foil, a, a, a, b, b, 6, connected at 
A and B, respectively, and separated from 
one another by sheets of oiled silk, or thin plates of mica. 
Conducting Power, Order of.— The ability of a given 
length and area of cross section of a substance to conduct 
electricity, as compared with an equal length and area of cross 
section of some other substance, such as pure silver or copper. 
No substance is known that does not offer some resistance 
to the passage of an electric current. 

The following table is taken from Sylvanus P. Thompson's 
" Elementary Lessons in Electricity and Magnetism :" 
Silver. _ 1 

SEmet^ 

Charcoal. J 

Water. "1 

The human body | 

Cotton 

Dry wood 

Marble 

Paper 

Oils.... 

Porcelain.. 

Wood 

Silk 

Eesins 

Gutta-percha 

Shellac 

Ebonite 

Paraffin... 

Glass 

Dry air 



V Partial conductors. 



M on- conductors. 



WORDS, TERMS AND PHRASES. 151 

Conductive Discharge.— (See Discharge, Conductive.) 

Conductor, Anisotropic —(See Anisotropic 

Conductor.) 

Conductor, Am i-Induction (See Anti-Induc- 
tion Conductor. 

Conductor, Conjugate "In a system of 

linear conductors, any pair of conductors are said to be con- 
jugate to one another when a variation of the resistance 
or the E. M. F. in the one causes no variation in the current 
of the other." {Brough.) 

Conductors, Isotropic (See Isotropic Con- 
ductor.) 

Conductors. — Substances which will permit the passage 
of an electric current through them. 

This term is opposed to non-conductors, or those which will 
not permit the passage of an electric current through them. 

Conduit, Electric, Underground A space or 

place for the reception of electric wires or cables. (See Sub- 
way, Electric.) 

Conservation of Energy. — The indestructibility of en- 
ergy. 

The total cmantity of energy in the universe is unalterable. 

The total energy of the universe is not, however, available 
for the production of useful work for man. 

When energy disappears in one form it reappears in some 
other form. This is called the correlation or conservation of 
energy. The commonest form in which energy reappears is 
as heat, and in this case some of the heat is lost to the earth by 
radiation. This degradation, or dissipation of energy causes 
some of the energy of the earth to become non-available to 
man. 

Energy is therefore available and non-available. (See En- 
tropy.) 



152 A DICTIONARY OF ELECTRICAL 

Consequent Magnet Poles.— The name given to the 
magnetic poles formed by two free N. poles or two free S. 
poles placed together. (See Anomalous Magnets.) 

Contact Electricity. — Electricity produced by the mere 
contact of dissimilar metals. 

The mere contact of two dissimilar metals results in the pro- 
duction of opposite electrical charges on their opposed sur- 
faces, or in a difference of electric potential between these 
surfaces. The mere contact of dissimilar metals cannot 
produce a constant electric current. An electric current 
possesses kinetic energy. To produce a constant electric cur- 
rent, therefore, energy must be expended. In the voltaic pile 
though the contact of dissimilar metals produces a difference 
of potential, yet the cause of the current is to be found in 
chemical action. (See Cell, Voltaic.) 

Contact-Series. — A series of metals arranged in such an 
order that each becomes positively electrified by contact with 
the one that follows it. 

The contact values of some metals, according to Ayrton 
and Perry, are as follows : 

Contact-Series. 

Difference of Potential in Volts. 

Zinc ) 

Lead f 

Lead _ / 

Tin J 

Tin I 

Iron j 

Iron ) 



..210 

069 

Iron..... f 313 



Copper f" --"- - 140 

H°aE m -:::::::::::l- *» 

Platinum - ) 1 1 Q 

Carbon............ ' 



WORDS, TERMS AND PHRASES. 153 

The difference of potential between zinc and carbon is equal 
to 1.089, and is obtained by adding the successive differences 
between them. 

This fact is known technically as V olio's Law, which may be 
formulated as follows : 

The difference of potential produced bytlie contact of any 
two metals is equal to the sum of the differences of potentials 
between the intervening metals in the contact series. 

Contact Theory of Voltaic Cell.— (See Cell, Vol- 
taic.) 

Contacts. — A variety of faults occasioned by the accidental 
contact of a circuit with any conducting body. 

Contacts of this character are of the following varieties, 
viz. : 

(1) Full, or Metallic, as when the circuit is accidentally placed 
in firm connection with another metallic circuit. 

(2) Partial, as by imperfect conductors being placed across 
wires, or bad earths, or defective insulation. 

(3) Intermittent, as by occasional contacts of swinging 
wires, etc. 

Contractures.— In electro-therapeutics, a prolonged mus- 
cular spasm, or tetanus, caused by the passage of an electric 
current. 

Controlling Clocks, Electric In a system of 

time telegraphy, the master clock, whose impulses move or 
regulate the secondary clocks. (See Clocks, Electric.) 

Controlled Clocks, Electrically In a system 

of time telegraphy, the secondary clocks, that are either driven 
or controlled by the master clock. (See Clocks, Electric.) 
Convection. Electric ; Convection Streams. 

—The air particles, or air streams, that are thrown off from 
the pointed ends of a charged, insulated conductor. 

Convection streams, like currents flowing through conduct- 
ors, act magnetically, and are acted on themselves by mag- 



154 A DICTIONARY OF ELECTRICAL 

nets. The same thing 1 is true of the brush discharge of the 
voltaic arc, and of convective discharges in vacuum tubes. 

Convection, Electrolytic A term proposed by 

Hehnholtz to explain the apparent conduction of electricity 
by an electrolyte, without consequent decomposition. 

Hehnholtz assumes that molecules of oxygen or hydrogen, 
adhering to the electrodes during electrolysis, are mechan- 
ically dislodged and diffused through the liquid, thus car- 
rying off the electricity by the charges received by them while 
in contact with the electrodes. 

Convection of Heat, Electric A distribution 

of heat during the passage of a current through an unequally 
heated conductor. 

If the central portions of a metallic bar are heated, the curve 
of heat distribution is symmetrical. On sending an electric 
current through the wire it is heated according to Joule's law, 
and the curve of heat distribution is still symmetrical. But 
the current in passing from the colder to the hotter parts of 
the wire produces an additional heating effect at this point, 
and in passing from the warmer to the colder parts of the 
wire, produces a cooling effect. (See Effect, Peltier. Effect, 
Thomson.) The curve of heat distribution is then no longer 
symmetrical. The term the Electrical Convection of Heat 
has been given to the dissymmetrical distribution of heat so 
effected. 

Sir Wm. Thomson, who studied these effects, found that 
the electrical convection of heat in copper takes place in the 
opposite direction to that in iron ; that is to say, the electrical 
convection of heat is negative in iron, (i. e. , the direction is 
opposite to that of the current) and positive in copper. 

Convective Discharge. — (See Discharge, Convective.) 

Converter, or Transformer. — The inverted induction 
coil employed in systems of distribution by means of alternat- 
ing currents. 



WORDS, TERMS AXD PHRASES. 



155 



A converter, or transformer, consists essentially of an induc- 
tion coil in which the primary wire, P P, Fig. 119, is long- and 
thin, and consequently of high electric resistance as compared 
with the secondary wire, S S, which is short, thick, and of low 
resistance. 




a ! 



! A 

! 
P 

i 1 



— 



£) 



Fig. 110. 

To prevent heating and loss of energy in conversion, the 
core is thoroughly laminated. To lower the magnetic 
resistance, the converter is iron-clad. 

In a system of electrical distribution by means of trans- 
formers, alternating currents, of small volume and compara- 
tively considerable difference of potential, are sent over a line 
from a distant station, and passing into the primary wire of a 
number of converters, generally connected to the line in mul- 
tiple-arc produce, by induction, currents of comparatively large 
volume and small difference of potential in the secondary 
wires. Various electro-receptive devices are connected in 
multiple-arc with the secondary wires. 



156 



A DICTIONARY OF ELECTRICAL 



This method of distribution greatly reduces the cost of the 
main conducting wires or leads in certain cases, since consider- 
able energy may be conveniently sent over a comparatively 
thin wire, if the difference of potential is sufficiently great. 

The general arrangement of the converters on the main 




Fig. 120. 



line, and the connection of the secondary circuits with the 
electro-receptive device in such a system, is shown in 
Fig. 120. The converters are supported on the line poles, 
as more clearly shown in Fig. 121, in which the termi- 
nals of the primary and secondary of the converter are readily 
seen. 

When the converter is properly constructed the loss of 
conversion is but small at full load ; that is to say, the watts in 
the secondary are very nearly equal to those in the primary. 
A current of 10 amperes, at 2000 volts, when passed into a 
converter, the number of whose turns in the primary is twenty 
times the number in its secondary, will produce in its sec- 
ondary, a current of 200 amperes at about 100 volts. Here, 
the number of watts in the two cases is exactly the same, 
or theoretically 20,000 watts. In reality, it is somewhat 



WORDS, TERMS AND RhRASES. 



157 



smaller. In gen- 
eral, the shorter 
the wire on the sec- 
ondary, and the 
smaller its number 
of turns, the great- 
er is the reduction 
in the difference of 
potential, and the 
greater is the cur- 
rent produced. 

Co-Ordinales, 
Axes of 

— The axes of ab- 
scissas and o r d i- 
nates. 

The two straight 
lines, perpendicu- 
lar to each other, 
to which distances 
representing v a 1- Fi $' 121 - 

ues are referred for the graphic representation of such values. 
(See Abscissas, Axis of.) 

Copper Bath.— (See Baths, Copper, etc.) 

Cords, Eleetric Flexible, insulated electric con- 
ductors, generally containing at least two parallel wires. 

They are named from the purposes for which they are em- 
ployed, battery cords, dental cords, lamp cords, motor cords, 
switch cords, etc. 

Core of Cable. — The conducting wires of an electric 
cable. (See Cable, Electric.) 

Core Ratio of Cable.— The ratio between the diameter 
of the insulator of a cable and the mean diameter of the 
strand. 




158 A DICTIONARY OF ELECTRICAL 

The core ratio is represented by -r ; where D, is the diam- 
eter of the insulator, and d, the mean diameter of the strand. 
Should the extreme diameter of the strand of a cable be used 
in calculations for insulation resistance, inductive capacity, 
etc., erroneous values would be obtained. The measured 
diameter of the copper conductor is consequently decreased 
some five per cent, by means of which the correct values are 
approximately given. (Clark & Sabine.) 

Cored Carbons.— (See Carbons, Cored.) 
Cores, Armature (See Armature Cores.) 

Cores, Armature, Ventilation of Means for 

the passage of fluids, such as air through the armature cores 
of dynamo-electric machines so as to prevent the undue ac- 
cumulation of heat. 

A properly proportioned dynamo-armature should need no 
ventilation, since in such the amount of heat generated is 
small as compared with the extent of the radiating surface. 

Cores, Lamination of Structural subdivisions of 

the cores of magnets, armatures, and pole pieces of dynamo- 
electric machines, electric motors, or similar apparatus, in 
order to prevent heating and subsequent loss of energy from 
the production of loecd, eddy or FoueauH currents. 

These laminations are obtained by forming the cores of 
sheets, rods, plates, or wires of iron insulated from one 
another. 

The cores of armatures should be divided in planes at right 
angles to the armature coils ; or in planes parallel to the di- 
rection of the lines of force and to the motion of the arma- 
ture ; or in general, in planes perpendicular to the currents 
that would otherwise be generated in them. 

Pole pieces should be divided in planes perpendicular to 
the direction of the currents in the armature wires. 



WORDS, TERMS AND PHRASES. 159 

Magnet cores should be divided in planes at right angles to 
the magnetizing current. 

Cosine. — One of the trigonometrical functions. (See 
Trigonometry.) 

Cotangent. — One of the trigonometrical functions. (See 
Trigonometry.) 

Coulomb. — The unit of electrical quantity. 

A definite quantity or amount of the thing or effect called 
electricity. 

Such a quantity of electricity as would pass in one second 
in a circuit whose resistance is one ohm, under an electro-mo- 
tive force of one volt. 

The quantity of electricity contained in a condenser of one 
farad capacity, when subjected to an electro-motive force of 
one volt. 

Coulomb- Volt. — A Joule, or .7373 foot pound. 
The term is generally written volt-coulomb. (See Volt- 
Coulomb.) 

Couiiter-Electro-UIotivc Force.— An opposed or re- 
verse electro-motive force produced in an electric source, 
which tends to produce a current in the opposite direction to 
that regularty produced by the source. 

In an electric motor, an electro-motive force contrary to 
that produced by the current which drives the motor, and 
which is proportional to the velocity attained by the motor. 

Counter-electro-motive force acts to diminish the current in 
the same manner as a resistance would, and is therefore 
sometimes called the spurious resistance in order to distin- 
guish it form the ohmic or true resistance. 

Counter-elect ro-mot ire force is sometimes expressed in 
ohms, though it is not true ohmic resistance. (See Spurious 
Resistance.) 

The counter-electro-motive force of a voltaic battery is due 
to the polarization of the cells. Since this force is due to the 



160 A DICTIONARY OF ELECTRICAL 

current in the cell, it can never exceed such current or reverse 
its direction. It may, however, equal it and thus stop its 
flow. (See Polarization of Voltaic Cell.) 

In a storage cell, the charging current produces an electro- 
motive force counter to itself, which, as in a motor, is a true 
measure of the energy stored in the cell. Economy requires 
that the electro-motive force of the charging current should 
be as little greater as possible than that of the counter-electro- 
motive force of the cell it is charging. 

In a voltaic arc a counter-elect'-'O-motive force is set up by 
polarization. 

Counters, Electric Various devices for count- 
ing and registering such quantities as the number of fares 
collected, gallons of water pumped, sheets of paper printed, 
revolutions of an engine per second, votes polled, etc. 

Various electric devices are employed 
for this purpose. They are, generally, 
electro-magnetic in character. 

Couple. — In mechanics, two equal 
parallel forces acting in opposite direc- 
tions and tending to cause rotation. 
The moment, or effective power of a 
s couple, is equal to the intensity of one of 

Fig. n%. the forces multiplied by the perpendicular 

distance between the directions of the two forces. 

Couple, magnetic The couple which tends to 

tarn a magnetic needle, placed in the earth's field, into the 
plane of the magnetic meridian. 

If a magnetic needle is in any other position than in the 
magnetic meridian, there will be two parallel and equal 
forces acting at A and B, Fig. 122, in the directions shown by 
the arrows. Their effect will be to rotate the needle until it 
comes to rest in the magnetic meridian N S. 

The total force acting on either pole of a needle free to 
move in any direction is equal to the strength of that pole 




WORDS, TERMS AND PHRASES. 161 

multiplied by the total intensity of the earth's field at that 
place, or, if free to move in a horizontal direction only, is 
equal to the intensity of the earth's horizontal component of 
magnetism at the place at which the needle is situated, multi- 
plied by the strength of that pole. 

The effective power or moment of the magnetic couple is 
equal to the force exerted on one of the poles multiplied by 
the perpendicular distance, P Q, between their directions. 

Couple, Tlienno-E lee trie Any two dissimi- 
lar metals which, when connected at their ends only, will 
produce an electric current when one set of ends is heated 
more than the other. 

Couple, Voltaic The two plates of dissimilar 

metals, or other substances in a voltaic battery which are 
immersed in the liquid of the cell, as for example, the zinc 
and copper plates of the simple voltaic cell. 

All voltaic cells have two metals, or a metal and a metal- 
loid, or two gaseous or liquid substances which are of such a 
character that, when dipped into the battery solution, one 
only is chemically acted on. 

Each of these substances is called an element of the cell, 
and the two taken collectively form a voltaic couple. 

The elements of a voltaic couple may consist of two gases 
or two liquids. (See Gas Battery. ) 

Coupling of Yoltaie Cells or Other Electric 
Sources. — A term indicating the manner in which a num- 
ber of separate electric sources are connected so as to form a 
single source. (See Circuits, Varieties of.) 

C. P. — A contraction frequently used for candle power. 
(See Candle, Standard.) 

Crater in Positive Carbon,— The depression at the 
end of the positive carbon which appeal's when a voltaic arc is 
formed. (See Arc, Voltaic.) 



162 A DICTIONARY OF ELECTRICAL 

Creo§oting. — A process employed for the preservation of 
wooden telegraph poles by injecting creosote into the pores of 
the wood. (See Pole, Telegraphic.) 

Creeping. — The formation of salts by efflorescence on the 
sides of the porous cup of a voltaic cell, on the walls of the 
vessel containing the electrolyte, or on the walls of any 
vessel containing a saline solution. 

Paraffining the portions of the walls out of the liquid, or 
covering the surface of the liquid with a neutral oil, obviates 
much of this difficulty. (See Efflorescence.) 

Critll. — A term proposed by A. W. Hoffman, as a unit of 
volume, or the volume of one litre, or cubic decimetre, of 
hydrogen at 0° C. and 760 mm. barometric pressure. 

Critical Current. — The current at which a certain result 
is reached. 

Critical Current of a Dynamo.— That value of the 
current at which the characteristic curve begins to depart 
from a nearly straight line. (Sylvanus P. Thompson.) 

As a rule the critical current of a dynamo 
occurs when the speed is such that the electro- 
motive force is nearly two-thirds the maximum 
value. 

In Fig. 123 the critical current is shown in 
three different cases, as occuring where the 
dotted vertical line cuts the characteristic 
curves. 

The speed at which a series dynamo excites 
itself is often called the critical speed. 

A connection, generally metallic, 

accidentally established between two conducting lines. 

A defect in a telegraph or telephone circuit caused by two 
wires coming into contact by crossing one another. 

A swinging or intermittent cross is caused by wires which 
are too slack, being occasionally blown into contact by the 
wind, 



WORDS, TERMS AND PHRASES. 163 

A weather cross arises from defective action of the insulators 
in wet weather. 

Crossing Wire§. — A device employed in telegraphic 
circuits whereby a faulty conductor of a telegraph line is cut 
out of the circuit by crossing over to a neighboring, less used, 
line. 

To cut out a faultv A B C D E 



section of wire in any 
circuit, such as C D, 
in the circuit ABC 
D E, Fig. 124, a cross 



Fig. 12k. 



connection is made to a line X Y, running near it, and which 
may be temporarily thrown out of use. By this means the 
interruption of an important circuit may be avoided. 

Crucible, Electric — — A crucible in which the heat 

of the voltaic arc, or of electric incandescence, is employed 
either to perform difficult fusions, or for the purpose of 
effecting the reduction of metals from their ores, or the forma- 
tion of alloys. (See Furnace, Electric.) 

Crystal. — A solid body bounded by symmetrically disposed 
plane surfaces. 

A definite form or shape is as characteristic of an organic 
substance, as it is of the animal or plant. Each substance has 
a form in which it generally occurs. There are, however, 
certain modifications of the typical form which cause plane 
surfaces to appear curved, and the symmetrical arrangement 
of the faces to disappear. These modifications often render 
it extremely difficult to recognize the true typical form. 

For the different fundamental crystalline forms, or systems 
of crystals, see any standard work on chemistry. 

Crystallization. — Solidification from a state of solution 
or fusion, with the assumption of definite crystalline forms. 

The crystallization of a dissolved solid is favored by any 
cause that gives increased freedom of movement to the par- 



164 A DICTIONARY OF ELECTRICAL 

tides of the solid, such for example as, solution, fusion, 
sublimation, or precipitation. 

Crystallization by Electrical Decomposition.— 

The crystalline deposition of various metals by the passage of 
an electric current through solutions of their salts under 
certain conditions. 

A strip of zinc immersed in a solution of sugar of lead, 
(acetate of lead) soon becomes covered with bright metallic 
plates of lead, that are electrically deposited by the weak 
currents due to minute voltaic couples (See Couple, Voltaic), 
formed with the zinc by particles of iron, carbon, or other 
impurities in the zinc. The deposit assumes at times a tree- 
like growth, and is therefore called a lead tree. 

Cube, Faraday's (See Net, Faraday's.) 

Current, Alternating or Reversed A cur- 
rent which flows alternately in opposite directions. 
A current whose direction is rapidly reversed. 
The non-commuted current generated by the differences of 
B potential in the armature of a 
/fljiiK dynamo-electric machine is an 
/ | ! j j | | \ alternating current. 
/I | j ;\ In a characteristic curve of the 
A C \ j J j j IE electro-motive forces of alternat- 
\1 | j j { ! j / m g currents, positive electro- 
\J! j | \y motive forces, or those that would 
q produce currents in a certain 
Fig. 125. direction, are indicated by values 
above a horizontal line, and negative electro-motive forces, 
by values below the line. 

The curves ABC and C D E, Fig. 125, are often called 
phases, and represent the alternate phases of the current. 

Current, Alternative or Voltaic Alterna- 
tives. — A term sometimes used in electro-therapeutics for 
a sudden alternating current. (See Alternatives, Voltaic.) 



WORDS, TERMS AND PHRASES. 165 

Current, Commuted The current of any elec- 
tric source which produces alternating currents, that have 
been caused to flow in one and the same direction by the aid 
of a commutator*. (See Commutator.) 

Current, Continuous An electric current which 

flows in one and the same direction. 

This term is used in the opposite sense to alternating cur- 
rent. 

Current, Critieal (See Critical Current.) 

Current Density The quantity of current which 

passes in any part of a circuit as compared with the area of 
cross section of that part of the circuit. 

In a dynamo-electric machine the current density in the ar- 
mature wire should not, according to Sylvanus P. Thompson, 
exceed 2,500 amperes per square inch of area of transverse 
section of conductor. 

In electro-plating, for every definite current strength that 
passes through the bath, a definite weight of metal is depos- 
ited, the character of which depends on the current density. 
The character of an electrolytic deposit will therefore depend 
on the current density at that part of the circuit where the 
deposit occurs. 

Current, Diaeritieal (See Diacritical Cur- 
rent.) 

Current, Direct A current constant in direction, 

as distinguished from an alternating current. 

Current, Electrie The quantity of electricity 

which passes per second through any conductor or circuit, or 
the rate at which a definite quantity of electricity passes or 
flows through a conductor or circuit. 

An electric current represents the ratio existing between 
tho. electro-motive force, causing the current, and the re- 
sistance which may be regarded as opposing it. This ratio 
is then expressed in terms of quantity of electricity per second. 



166 A DICTIONARY OF ELECTRICAL 

The unit of current or the ampere is equal to one coulomb 
per second. (See Ampere. Coulomb.) 

The word current must not be confounded with the mere 
act of flowing-; electric current signifies rate of flow, and 
always supposes an electro-motive force to produce the cur- 
rent and a resistance to oppose it. 

The electric current is assumed to flow out from the positive 
terminal or of a source, through the circuit and back into the 
source at the negative terminal, and is assumed to flow into 
the positive terminal of an electro-receptive device such 
as a lamp, motor, or storage battery, and out of its nega- 
tive terminal; or, in other words, the positive pole of the source 
is always connected to the positive terminal of the electro-re- 
ceptive device. 

Current, Element of A term employed in 

mathematical discussions, to indicate a very small part of a 
current in considering its action on a magnetic needle or other 
similar body. 

Current, Faradic (See Faradic Current.) 

Current Induction.— (See Voltaic Induction. Electro- 
Dynamics.) 
Current, Intensity of. — (See Intensity of Current.) 
Current meter. — (See Galvanometer.) 

Current, Reversed A current whose direction 

is changed at intervals. (See Current, Alternating.) 

Current Re vers er. — A switch, or other apparatus, to re- 
verse the direction of a current. 

Currents, Amperian -(See Amperian Currents. 

Magnetism, Ampere's Theory of.) 

Currents, Diaphragm — (See Diaphragm Cur- 

rents.) 

Currents, Earth ■ -(See Earth Currents.) 



WORDS, TERMS AND PHRASES. 



167 



Currents, Eddy, Local, Foucault, or Parasit- 
ical Useless currents produced in the metallic 

masses of the pole pieces, armatures, or field magnet cores of 
dynamo-electric machines or motors, either by the motion of 
these parts through magnetic fields, or by the variations in 
the strength of electric currents flowing near them. 

Eddy currents may even be produced in the mass of the 
conducting wire on the armature, when this is compara- 
tively heavy. 

These currents are called eddy currents, local currents, 
Foucault currents, or parasitical currents. They form closed 
circuits of comparatively low resistance, and tend to cause 
undue heating of armatures or pole pieces. They not only 
cause a useless expenditure of energy, but interfere with the 
proper operation of the device. 

To reduce them as much as practicable, the pole pieces and 
armature cores are laminated. (See Cores, Lamination of.) 

Since eddy 
currents in dy- 
n a m o - electric 
machines are 
due to v a na- 
tions in the mag- 
net i c strength 
of the field mag- Fig. 126. 

nets, or of the armature, they will be of greatest intensity when 
the changes in the magnetic biiength are the greatest and most 
sudden. 

These changes are most marked, and consequently the eddy 
currents are particularly strong, at those corners of the pole 
pieces of a dynamo from which the armature is moved in its 
rotation, as will be seen from an inspection of Fig. 126. 

Fig. 127, shows eddy currents generated in pole pieces. 






168 



A DICTIONARY OF ELECTRICAL 




Currents, Extra.— In a coil of wire through which a cur- 
rent is passing, the current produced by the inductive action 
of the current on itself at the moment of breaking or mak- 
ing the circuit. 
The extra cur- 
rent induced on 
breaking flows in 
the same direct- 
ion as the original 
current and acts 
to strengthen and 
prolong it. 
The extra cur- 
rent induced on making or completing a circuit, is in the 
opposite direction, tending to oppose or retard the current. 

Both of these currents are called induced or extra currents. 
The former is called the direct-induced-current, and the latter 
the reversed-induced-current. 

In order to distinguish this induction from that produced in 
a neighboring conductor by the passage of the electric cur- 
rent, it is called self-induction. 

The effect of the self -induced or extra currents on tele- 
graphic line is to influence the speed of signaling by retard- 
ing the beginning of a signal, and prolonging its termina- 
tion. 



Fig. 127. 



magnet, and the greater the mass of iron in its core, the 
greater the strength of the extra current. 

Currents, X at lira 1 A term sometimes applied to 

earth currents. (See Earth Currents.) 

Currents, Negative and Positive A term em- 
ployed in telegraphy for currents sent over a line in a positive 
or a negative direction, respectively. (See Telegraph, Single- 
Needle.) 



WORDS, TERMS AND PHRASES. 169 

Currents, Orders of Induced electric currents 

named from the order in which they are induced, as currents 
of the first, second, third, fourth, etc., orders. 

An induced current can be caused to induce another current 
in a neighboring- circuit, and this a third current, and so on. 
Such currents are distinguished by the term, currents of the 
second, third, fourth, etc., order. (See Coils, Henry's.) 

Currents, Rectilinear — Currents flowing 

through straight or rectilinear portions of a circuit. 

In studying the effects of attraction or repulsion produced 
by electric currents, the peculiarity of shape of any part of 
the circuit is often applied to the current flowing through that 
circuit. 

Currents, Sinuous A term sometimes applied to 

currents flowing through a sinuous conductor. 

Sinuous currents exert the same effects of attraction or 
repulsion on magnets, or on other circuits, as would a rec- 
tilinear current whose length is that of the axis of such 
current. 

This can be shown by approaching the circuit A'B', Fig. 
128, consisting of the sinuous conductor A', and rectilinear 
conductor B', to the movable conductor ABC on which it 
produces no effect. The current A', therefore, neutralizes the 
effects of the current B'; or, it is equal to it in effect. 

In calculating the effects of sinuous currents, it is convenient 
to consider them as consisting of a succession of short, straight 
portions at right angles to one another, as shown in Fig. 129. 

Currents, ITndulatory Currents the strength 

and direction of flow of which gradually change. 

The currents produced by all alternate current dynamos are 
not of the character generally known as pidsatory, in which 
the strength and direction change suddenly. In actual 
practice, such currents differ from undulatory currents more 
in degree than in kind, since, when sent into a line, the effects 



170 



A DICTIONARY OE ELECTRICAL 



of retardation tend to obliterate, to a greater or less extent, 
the marked differences in intensity on which their undulatory 
character depends. 

The currents produced 
in the coils of the Sie- 
mens' magneto - electric 
key, in which the me- 
chanical to-and-fro mo- 
tion of the key sends 
electrical impulses into 
the line, are, in point 
of fact, undulatory in 
character when they fol- 
low one another rapidly. 

The currents in most 
dynamo- electric ma- 
chines, the number of 
whose armature coils is 
comparatively great, are, 
so far as the variations in their intensity or strength are con- 
cerned, undulatory in character even when non-commuted. 

The currents on all telephone lines that transmit articulate 
speech are undulatory. This is true, whether the transmitter 
employed merely varies the resistance by variations of pres- 
sure, or actually employs makes-and-breaks that rapidly fol- 
low one another. 

b ^> Jl 




Fig 




Curve, Ballistic (See Ballistic Curve.) 

Curves, Characteristic (See Characteristic 

Curves.) 



WORDS, TERMS AND PHRASES. 171 

Cut-Out, Automatic for Multiple Connected 

Electric Lamps. — A device for automatically cutting a 
lamp out of the circuit of the leads. 

Automatic cut-outs for incandescent lamps when connected 
to the leads in multiple-arc, consist of strips of readily melted 
metal called safety fuses, which on the passage of an 
abnormal current fuse and thus automatically break the cir- 
cuit in that particular branch. (See Safety Catch.) 

Cut-Out, Automatic for Series Connected 

Lamps. — A device whereby an electric arc lamp is, to all in- 
tents and purposes, automatically cut out, or removed from the 
circuit, by means of a shunt of low resistance, which permits 
the greater part of the current to flow past the lamp. 

It will be observed that the lamp is still in the circuit, but is 
to all practical intents cut out from the same, since the pro- 
portion of the current that now passes through it is too 
small to operate it. 

In most series arc lamps the automatic cut-out is operated by 
means of an electro-magnet placed in a shunt circuit of high 
resistance around the carbons. 

If the carbons fail to properly feed, the arc increases in 
length and consequently in resistance. More current passes 
through the shunt magnet, until finally, when a certain pre- 
determined limit is reached, the armature of the electro-mag- 
net is attracted to the magnet pole and mechanically com- 
pletes the short circuit past the lamp. 

In some automatic cut-outs the fusion of a readily fused 
wire, placed in a shunt circuit around the carbons, permits a 
spring to complete the short circuit. 

The automatic cut-out prevents the accidental extinguishing 
of any single lamp in a series circuit from extinguishing the 
entire circuit. 

Cylindrical Carbon Electrodes. — (See Carbons, 
Cored.) 



172 A DICTIONARY OF ELECTRICAL 

Cymogene. — An extremely volatile liquid which is given 
off from crude coal-oil during the early parts of its distillation. 

The two liquids which are obtained from the condensation of 
the vapors given off during the first parts of the distillation of 
crude coal oil are called cymogene, and rhigolene. These 
liquids are employed on account of their extreme volatility 
for the artificial production of cold. 

Rhigolene is employed by some for the treatment or flash- 
ing of the carbons used in incandescent lamps. (See Flashing, 
Method of.) 

Damping. — The act of bringing a swinging magnetic 
needle quickly to rest, so as to determine its amount of deflec- 
tion, without waiting until it comes to rest after repeated 
swingings to and fro. 

Damping devices are such as offer resistance to quick motion, 
or high velocities. Those generally employed in electrical ap- 
paratus are either air or fluid friction, obtained by placing vanes 
on the axis of rotation, or by checking the movements of the 
needle by means of the currents it sets up, during its motion, 
in the mass of any conducting metal placed near it. These 
currents, as Lenz has shown, always tend to produce motion 
in a direction opposed to that of the motion causing them. 
Bell-shaped magnets are especially suitable for this kind of 
damping. (See Magnet, Bell-Shaped.) 

The needle of a galvanometer is dead-beat, when its moment 
of inertia is so small that its oscillations in an intense field 
are very quick, and die out very rapidly, and the needle there- 
fore moves sharply over the scale from ftoint to point and 
comes quickly to a dead stop. 

Darnell's Voltaic Cell— (See Cell, Voltaic.) 

Dash-Pot. — A mechanical device to prevent too sudden 
motion in a movable part of any apparatus. 

The dash-pot of an automatic regulator, or of an arc-lamp, is 
provided to avoid too sudden movements of the collecting 
brushes on the commutator cylinder, or the too sudden fall of 



WORDS, TERMS AXD PHRASES. 173 

the upper carbon. Such devices consist essentially of a loose 
fitting* piston that moves through air or glycerine. 

Dash-pots are species of damping devices, and, like the damp- 
ing arrangements on galvanometers or magnetic needles, 
prevent a too free movement of the parts with which they 
are connected. (See Damping.) 

Dead - Beat Galvanometer. — (See Galvanometer, 
Dead Beat.) 

Dead Earth.— (See Earths.) 

Dead Turn§ of Armature Wire, or Dead Wire. 
— That part of the wire on the armature of a dynamo-electric 
machine which produces no useful electro-motive force, or 
resultant current, on movement of the armature through the 
magnetic field of the machine. 

The wire on the inside of a Gramme or ring armature, is 
dead-wire. 

Dead-Wire§. — Disused and abandoned electric wires. 

The term dead is often applied to a wire through which no 
current is passing. The term, however, is more properly 
applied to a wire formerly employed, but subsequently aban- 
doned. 

Dead wires in the neighborhood of active wires are a con- 
stant menace to life and property, and should invariably be 
carefully removed. 

It is often a matter of considerable importance to be able to 
determine whether or not a current is passing through a wire. 
When the wire is not inclosed in a moulding, or fastened 
against a wall, this can readily be ascertained by bringing a 
small compass needle near the wire, when it will tend to set 
itself across the wire. 

The term dead wire, as will be seen, is used in two distinct 
senses. 

Death, Electrical Death resulting from the 

the passage of the electric current through the human body. 



174 A DICTIONARY OF ELECTRICAL 

The exact manner in which an electric current causes death 
is not known. When the current is sufficiently powerful, as 
in a lightning flash, or a powerful dynamo current, insensi- 
bility is practically instantaneous. 

Death may be occasioned — 

(1) As the direct result of physiological shock. 

(2) From the action of the current on the respiratory centres. 

(3) From the actual inability of the nerves or muscles, or 
both, to perform their functions. 

(4) From an actual electrolytic decomposition of the blood or 
other tissues of the body. 

(5) From the polarization of those parts of the body through 
which the current passes. 

(6) From an actual rupture of parts by a disruptive discharge. 
The current required to cause death will depend on a variety 

of circumstances, among which are : 

(1) The particular path the current takes through the body, 
with reference to the vital organs that may lie in this path. 

(2) The freedom or absence of sudden variations of electro- 
motive force. 

(3) The time the current continues to pass through the body. 
In most fatal cases, it is probably the extra-current, or 

the induced direct current on breaking, that causes death, 
since, as is well known, its electro-motive force may be 
many times greater than that of the original current. 

A comparatively low potential continuous current, cannot, 
therefore, be properly regarded as entirely harmless, simply 
because its electro-motive force is comparatively small. 

Deci (as a prefix). — The one-tenth. 

Deci-L«ux.— The one-tenth of a lux. (See Lux.) 

Declination, or Variation of Magnetic Xeedle. — 

The deviation of the magnetic needle from the true geograph- 
ical north. 
This is often called the variation of the magnetic needle. 



WORDS, TERMS AND PHRASES. 175 

The declination of the magnetic needle is either E. or W. 
(See Angle of Declination.) 

The declination, or variation, is different for different parts 
of the earth's surface. 

Lines connecting' places which have the same value and 
direction for the declination are called isogonal lines. A chart 
on which the isogonal lines are marked is called a variation 
chart. (See Variation Chart.) 

The value of the declination varies at different times. 
These variations of the declination are : 

(1) Secular, or those occurring during [great intervals of 
time. Thus in 1580, the magnetic needle in London, had a 
variation of about 11° East. This eastern declination de- 
creased in 1622, to 6° E., and in 1680, the needle pointed to the 
true north. In 1692, the declination was 6° W.; in 1730, 13° 
W.; in 1765, 20° W.; and in 1818, the needle reached its great- 
est western declination and is now moving eastwards. The 
declination, however, is still west. 

(2) Annual, the needle varying slightly in its declination 
during different seasons of the year. 

(3) Diurnal, the needle varying slightly in its declination 
during different hours of the day. 

(4) Irregular, or those which occur during the prevalence 
of a magnetic storm. 

It has been discovered that the occurrence of a magnetic 
storm is simultaneous with the occurrence of an unusual num- 
ber of sun spots. (See Sun Spots.) 

Declinometer. — A magnetic needle suitably arranged for 
the measurement of the value of the magnetic declination or 
variation, of any place. 

Decomposition. — In chemistry, the separation of a mole- 
cule into its constituent atoms or groups of atoms. (See Mole- 
cule. Atom.) 

Decomposition, Electric or Electrolytic 

— The separation of a molecule into its constituent atoms 



176 A DICTIONARY OF ELECTRICAL 

or groups of atoms by the action of the electric current. 
These atoms or groups of atoms are either electro-positive 
or electro-negative in character. (See Electrolysis. Anion. 
Kathion.) 

Deflagration of Metals, Electrical 

The heating of metallic substances by the electric current 
to a temperature at which they rapidly fuse and volatilize. 

Deflagral or, Hare's The name given to a 

voltaic battery, of small internal resistance, employed by Hare 
in the deflagration of metals by the electric current. 

Deflection of magnetic Needle— The movement of 
a needle out of a position of rest in the earth's magnetic field, 
or in the field of another magnet, by the action of an electric 
current, or another magnet. 

Deflection Method. — A method employed in electrical 
measurements, as distinguished from the zero method, in 
which a deflection produced on any instrument by a given 
current, or by a given charge, is utilized for determining the 
value of that current or charge. 

The conditions remaining the same, the same current or 
charge will produce the same deflection at any time. Differ- 
ent deflections produced by currents or charges, the values of 
which are unknown, are determined by certain ratios existing 
between the deflections and the currents or charges. These 
ratios are determined experimentally by the calibration of the 
instrument. (See Calibration.) 

Deflection methods are opposed to zero or null methods, in 
which latter a balance of opposite electro-motive forces, or a 
proportionally equal fall of electric potential, is ascertained by 
the failure of a needle to be moved by a current or a charge. 

Degradation of Energy. — Such a dissipation of energy 
as to render it non-available to man. (See Conservation of 
Energy. Entropy.) 

Deka (as a prefix). — Ten times. 



WORDS, TERMS AND PHRASES. 177 

Demagnetization. — A process generally directly oppo- 
site to that for producing a magnet, by means of which the 
magnet may be deprived of its magnetism. 

A magnet may be deprived of its magnetism, or be demag- 
netized — 

(1) By heating it to redness. 

(2) By touching to its poles magnet poles of the same name 
as its own. 

(3) By reversing the directions of the motions by which its 
magetism was originally imparted, if magnetized by touch. 

(4) By exposing it in a helix to the influence of currents 
which will impart magnetism opposite to that which it origi- 
nally possessed. 

Demagnetization of Watche§. — (See. Watches, De- 
magnetization of.) 

Density of Charge.— (See Charge, Density of '.) 

Density of Current. — (See Current, Density of.) 

Density, Hagnetie (See Magnetic Density.) 

Dental Mallet, Electro-Hagnetie A mal- 
let for filling teeth, the blows of which are struck by means 
of electrically driven mechanism. 

Electro-magnetism was first employed for this purpose by 
Bonwill of Philadelphia. 

Depolarization. — The act of breaking up or removing 
the polarization of a voltaic cell or battery. (See Polarization 
of Voltaic Cell.) 

Deposit, Eleetro-Metallurgieal The deposit 

of metal obtained by electro-metallurgical processes. 

To obtain a good metallic deposit the density of the current 
must be regulated according to the strength of the metallic 
solution employed. 

Electro-metallurgical deposits are ejther— - 



178 A DICTIONARY OF ELECTRICAL 

(1) Reguline, or flexible, adherent, and strongly coherent 
metallic films, deposited when neither the current nor the 
solution is too strong. 

(2) Crystalline, or non-adherent and non-coherent deposits. 

The crystalline deposit may either be of a loose, sandy char- 
acter, which is thrown down when too feeble a current is used 
with too strong a metallic solution, or it may consist of a black 
deposit, which is thrown down when the current is too strong as 
compared with the strength of the solution. This latter char- 

q acter of deposit is sometimes technically 

called burning, and takes place most fre- 
quently at sharp corners and edges, where the 
current density is greatest. (See Density of 
Current.) 

Derived Circuit.— A term applied to a 
shunt circuit. 

If the conductor S, Fig. 130, be connected 
with the circuit of the battery B, a derived 
F,g. 130. circuit will thus be established, and a current 

will flow through S, thus diminishing the current in the gal- 
vanometer. (See Shunt Circuit.) 
Derived Units.— (See Units, Derived.) 
Destructive Distillation.— (See Distillation, Destruc- 
tive.) 

Device, Safety for multiple Circuits.— (See 

Safety Catch.) 

Device, Safety for Series Circuits.— (See 

Device, Safety, for Arc Lamps.) 

Device, Electro-Receptive Various devices 

placed in an electric circuit, and energized by the passage 
through them of the electric current. 

The following are among the more important electro-recep- 
tive devices, viz. : 

(1) Electro-Magnet. 

(2) Electric Motor, 




WORDS, TERMS AND PHRASES. 



179 



(3) An Arc or Incandescent Lamp. 

(4) An Uncharged Storage Cell. 

(5) An Electric Heater. 

(6) A Plating Bath, or Voltameter. 

(7) A Telegraphic or Telephonic Instrument. 

(8) Electro-Magnetic Signal Apparatus. 

Dextrorsal Helix. — (See Helix, Dextrorsal.) 

Diacritical Current. — Such a strength of the magnetiz- 
ing current as produces a magnetization of an iron core equal 
to half saturation. 




Fig. 131. 



Diacritical Number. — Such a number of ampere-turns 
at which a given core would receive a magnetization equal to 
half saturation. 

Diacritical Point of Magnetic Saturation.— A term 

proposed by S. P. Thompson for such a value of the coefficient 
of magnetic saturation, that the core is magnetized to exactly 
one-half its possible maximum of magnetization, 



180 A DICTIONARY OF ELECTRICAL 

Diagnosis, Electro The determination of the 

healthy or diseased condition of different parts of the human 
body by the character and extent of the muscular contrac- 
tions on electrical excitation of the nerves or muscles. 

Diagometer, Rousseau's An apparatus 

in which an attempt is made to determine the chemical com- 
position and consequent purity of certain substances by their 
electrical conducting powers. 

The arrangement of the apparatus is shown in Fig. 131. A 
dry pile A, has its negative, or — , terminal m', grounded. Its 
positive, or -f-, terminal is connected to a delicately supported, 
and slightly magnetized needle M, terminated by a conducting 
plate L. Opposite L, and at the same height, is a fixed plate 
of slightly larger size. The needle M, when at rest in the 
plane of the magnetic meridian, is in contact at L with the 
fixed plate. If, therefore, the upper plate of the pile is con- 
nected with the needle M both plates are similarly charged 
and repulsion takes place, the needle coming to rest at a 
certain distance from the fixed plate. 

The substance whose purity is to be determined is placed in 
the cup G, which is connected through L with the fixed plate. 
A branch wire from the -\- terminal of the pile is then dipped 
into the substance in G, and -ts purity determined from the 
length of time required for the two plates at L to be dis- 
charged through the material in G, 

It is claimed that the instrument will detect the difference 
between pure coffee and chicory. Its practical application, 
however, is very doubtful. 

Diagram. Thermo-EIectric A diagram in 

which the thermo-electric power between different metals is 
designated for different temperatures. 

The differences of potential, produced by the mere contact of 
two metals, varies, not only with the kind of metals, and the 
physical state of each metal, but also with their temperature. 
This difference of potential, maintained in consequence of 



WORDS, TERMS AND PHRASES. 



18i 



Q°c 50°c 100°c 150°c 200°c 250°c 300°c 350°c 400°c 450°c 



500 

O 




























Lead 






A' 




130 

500 

ionn 






B 


_Cof 


per 
















V°£ 








B' 












A 












1734 


' 



















the difference of temperature between the junctions of a 
thermo-electric couple, is approximately proportional to the 
differences of temperature of these junctions, if these dif- 
ferences are not great, and is equal to the product of such 
differences of temperature and a number dependent on the 
metals in the couple. This number is called the thermo- 
electric power. (See 
Couple, Thermo-Elec- 
tric. Thermo- Electric 
Power.) 

In Fig. 132 (after 
Tait), the thermo- 
electric power is 
shown between lead Fig. 132. 

and iron, and lead and copper. The numbers at the top of the 
table represent degrees of the Centigrade thermometer. 
Those at the sides represent the differences of potential in 
micro-volts. 

The thermo-electric power of the lead-iron couple decreases 
from the freezing point of water, 0° C, to a temperature of 
274°. 5 C, when it becomes zero. Beyond that temperature 
the thermo-electric power increases, but in the opposite 
direction. The point at which this occurs is called the neu- 
tral point. 

Dial Telegraph.— (See Telegraphy, Step-by-Step.) 

Diamagnetie. — A term applied to the property possessed 
by substances like bismuth, phosphorus, antimony, zinc and 
numerous others, which are apparently repelled when placed 
between the poles q£ powerful magnets. 

"When diamagnetic substances in the form of rods or bars 
are placed, as in Fig. 134, between the poles A and B of a 
powerful electro-magnet, they place themselves at right 
angles to the poles, or are apparently repelled. 



182 



A DICTIONARY OF ELECTRiCAL 




Paramagnetic substances like iron or steel, on the contrary, 
come to rest under similar circumstances in a straight line 
joining; the poles, as in the position shown in the annexed 
/^\ figure. 

Paramagnetic substances are some- 
times called ferro - magnetic, or sub- 
stances magnetic after the manner of 
iron. This word is unnecessary and ill. 
advised. The term sidero-magnetic has 
also been proposed in place of paramag- 
netic. 

Paramagnetic substances appear to 
concentrate the lines of magnetic force 
on them; that is, their magnetic resist- 
ance is smaller than that of the air or 
other medium in which the magnet is 
Fig. 1SU. placed. They therefore come to rest 

with their greatest dimensions in the direction of the lines of 
magnetic force. 

Diamagnetic substances appear to have a greater magnetic 
resistance than that of the air around them. They therefore 
come to rest with their least dimensions in the direction of 
the lines of magnetic force. 

The difference between paramagnetic and diamagnetic sub- 
stances is believed by some to be due to the resistance they 
thus offer to lines of magnetic force as compared with that 
offered by air or by a vacuum. 

The action of magnetism, however, on gaseous media, ro- 
tating a plane of polarized light to the right, in some gases, 
and to the left in others, shows that the real nature of these 
phenomena is yet unknown. 

Tyndall comes to the conclusion as the result of extended 
experimentation, " that the diamagnetic force is a polar force, 
the polarity of diamagnetic bodies being opposed to that of 



WORDS, TERMS AND PHRASES. 



183 



paramagnetic ones under the same conditions of excitement." 
(See Tyndall, on Diamagnetism.) 

Diamagnetism is also possessed by certain liquid and gas- 
eous substances. 

Diamagnetic Polarity. — (See Polarity, Diamagnetic.) 

Diainagneti§m. — A term applied to the magnetism of dia- 
magnetic bodies. (See Diamagnetic.) 

Diameter of Commutation. — In a dynamo-electric 
machine, a diameter on the commutator cylinder on one 
side of which the differences of potential, produced by the 
movement of the coil through the magnetic field, tend to pro- 
duce a current in a direction 
opposite to those on the 
other side. 

Tims, in Fig. 133, the di- 
rections of the induced elec- 
tro-motive forces are indi- 
cated by the arrows. The 
diameter of commutation is 
therefore the line n n' . The 
term neutral line is also 
sometimes given to this line. Fig. 133. 

It lies at right angles to the line of maximum magnetization. 

In an armature with closed-circuited coils, that is, in an 
armature in which the armature coils are connected in a 
closed circuit, the collecting brushes rest on the commutator 
cylinder at the neutral line, or on the diameter of commuta- 
tion. 

In an open circuited armature, however, where the coils 
are independent of each other, the collecting" brushes must be 
set at in m, at right angles to the neutral line n n. The term 
diameter of commutation is, therefore, often applied to this 
second position. According to this use of the term, the diame- 
ter of commutation is that diameter on the commutator 
which joins the points of contact of the collecting brushes. 




184 A DICTIONARY OF ELECTRICAL 

The neutral line n n, Fig. 133, it will be noticed does not 
occupy a vertical position, but is displaced somewhat in the 
direction of rotation, thus necessitating the shifting of the 
brushes forward in the direction of rotation. This necessary 
shifting of the brushes is known technically as the Lead of the 
Brushes. (See Angle of Lead.) 

It will thus be seen that the term diameter of commutation 
is used in different senses. 

In reality, the term refers to the position of certain points 
on the commutator as distinguished from points on the arma*- 
ture coils. On the commutator, the diameter of commutation 
is the line drawn through the two commutator bars at which 
the currents from the two sides are opposed to each other. 

It is evident that the commutator may be intentionally 
twisted with respect to the armature, so as to bring its diam- 
eter of commutation into any desired convenient position. 

Diaphragm. — A sheet of some solid substance, generally 
elastic in character and circular in shape, securely fixed at its 
edges and capable of being set into vibration. 

The receiving diaphragm of a telephone is generally a rigid 
plate or disc of iron fixed at its edges, placed near a magnet 
pole, and set into vibration by variations in the magnetic 
strength of the pole due to variations in the current that is 
passed over the line. 

The diaphragm of the transmitting telephone, or of a pho- 
nograph, consists of a plate, fixed at its edges and set into 
vibration by the sound waves striking it. 

Diaphragm Currents. — Electric currents produced by 
forcing a liquid through the capillary pores of a diaphragm. 
(See Osmose, Electric.) 

Diaphragm of Voltaic Cell.— A term sometimes 
used for the porous cell of a double fluid voltaic cell. (See 
Porous Cell. Cell, Voltaic.) 

Dielectric. — A substance which permits induction to take 
place through its mass. 



WORDS, TERMS AND PHRASES. 185 

The substance which separates the opposite coatings of a con- 
denser is called the dielectric. All dielectrics are non-con- 
ductors. 

All non-conductors or insulators are dielectrics, but their 
dielectric power is not exactly proportional to their non-con- 
ducting power. 

Substances differ greatly in the degree or extent to which 
they permit induction to take place through or across them. 
Thus, a certain amount of inductive action takes place 
between the insulated metal plates of a condenser across the 
layer of air between them. 

Dielectric Capacity, or Dielectric Constant.— A 

term employed in the same sense as specific inductive 
capacity. (See Capacity, Specific Inductive.) 

Dielectric Strain. — The strained condition in which the 
glass, or other solid dielectric of a condenser, is placed by the 
charging of the condenser. 

The stress in this case, i. e., the force producing the defor- 
mation or strain, is the attraction of the opposite charges. 
This stress, in the case of a Leyden jar, is often sufficiently 
great to cause a rupture of the glass. 

Difference of Potential. — A term employed to denote 
that portion of the electro-motive force which exists between 
any two points in a circuit. 

The difference of potential at the poles of any electric source, 
such as a battery or dynamo, is that portion of the total elec- 
tro-motive force which is available, and is equal to the total 
electro-motive force, less what is lost in the source. (See 
Potential. Electro-Motive Force.) 

Differential Galvanometer.— A galvanometer in 
which the needle is deflected by the action of two parallel 
coils, the currents in which are opposed to each other. (See 
Galvanometer, Differential.) 



186 



A DICTIONARY OF ELECTRICAL 



Differential Inductometer.— (See Inductometer, Dif- 
ferential.) 

Differential Thermo-Pile.— A thermo-pile in which 
both faces of the pile are exposed to the action of two nearly 
equal sources of heat in order to determine accurately the 
difference in their intensities. (See Thermo-Pilc.) 

Differential Voltameter. — (See Voltameter, Differen- 
tial.) 

Diffusion of Electric Current.— A term employed 
mainly in electro-therapeutics to designate the difference in 
the density of current in different portions of the human 
body, or other conductor. 

When the electrodes are placed at any two given points of 
the human body, the current branches through various paths, 

extending in a general direction 
from one electrode to the other, 
according to the law of branch 
or derived circuits, and flowing 
in greater amount, or with 
greater density of current, 
through the relatively better 
conducting paths. (See Den- 
sity of Current.) 

Dimensions of Acceler- 

a t i © n . — (See Acceleration, 
Unit of.) 

Dip, Magnetic 

The deviation of the magnetic 
needle from a horizontal posi- 
tion. 

The inclination of the mag- 
netic needle towards the earth. 
The magnetic needle shown 
in Fig. 135, though supported at its centre of gravity will not 
retain a horizontal position in all places on the earth's surface. 




WORDS, TERMS AND PHRASES. 



187 



In the Northern Hemisphere its north-seeking end will dip 
or incline at an angle B O C, called the angle of dip. In 
the Southern Hemisphere its south-seeking end will dip. 

The cause of the dip is the unequal distance of the mag- 
netic poles of the earth from the poles of the needle. 

The Magnetic Equator is a circle passing around the earth 
midway (in intensity) between the earth's magnetic poles. 
There is no dip at the magnetic equator. At either magnetic 
pole the angle of dip is 90°. 

Dipping Circle, or Inclination Compass.— A mag- 
netic needle moving freely in a 
single vertical plane, and em- 
ployed for determining the an- 
gle of dip at any place. 

The needle M, Fig. 136, is sup- 
ported on knife edges so as to 
be free to move only in the 
vertical plane of the graduated 
vertical circle C O. This circle 
is movable over the horizon- 
tal graduated circle H H. In 
order to determine the true 
angle of dip, the vertical plane 
in which the needle is free to 
move must be placed exactly 
in the plane of the magnetic 
meridian. 

To ascertain this plane the Fig. 186. 

vertical circle is moved until the needle points vertically 
downwards. It is then in a plane 90° from the magnetic 
meridian. The vertical circle is then moved over the hori- 
zontal circle 90°, in which position it is in the plane of the 
magnetic meridian, when the true angle of dip is read off. 

For an explanation of the reason of this see Component, 
Horizontal and Vertical, of the Earth's Magnetism. 




188 A DICTIONARY OP ELECTRICAL 

Dipping, Electro-Metallurgical Deposition by 

The process of obtaining a metallic deposit on a 



metallic surface by dipping- it in a solution of a readily decom- 
posable metallic salt. 

A bright, polished iron surface, when simply dipped into a 
solution of copper sulphate, receives a coating of metallic cop- 
per from the electrolytic action thus set up. 

This process is known technically as dipping. The term 
dipping is also used in electro-metallurgy to indicate the pro- 
cess of cleaning the articles that are to be electro-plated by 
dipping them in various acid or alkaline baths. 

Direct Current. — (See Current, Direct.) 

Direct Induced Current.— The current induced in a 
circuit by induction on itself, or self induction, on breaking 
the circuit. (See Extra Current.) 

Direction of Lines of Force. — The direction in which 

it is assumed the lines of 
magnetic force pass. 

It is generally agreed to 
consider the lines of mag- 
netic force as coming out 
of the north pole of a mag- 
net and passing into its 
south pole, as shown in 
Fig. 137. Fig. 137. 

This is sometimes called the positive direction of the lines 
of force, and agrees in general with the direction in which 
the electric current is assumed to flow, which is from the 
positive to the negative. That is to say, the lines of mag- 
netic force are assumed to flow or pass out of the north pole 
and into the south pole of a magnet. Of course there is no 
evidence of any flow, or any particular direction as character- 
izing them. (See Field, Magnetic.) 




WORDS, TERMS AND PHRASES. 



189 



Directive Power of Magnetic Needle.— The ten- 
dency of a magnetic needle to move so as to come to rest in 
the direction of the lines of the earth's magnetic field. 

The directive power of the needle is due to the attraction of 
the earth's magnetic poles for the poles of the needle, or to 
Hie action of the earth's magnetic field. Since the force of 
the earth's magnetism forms a couple, there is no tendency 
for the needle to move towards either of the earth's poles, 
but merely to rotate until it comes to rest with the lines of 
the earth's magnetic field passing through its poles. (See 
Couple, Magnetic.) 

Of course this would be true in the case of a directing mag- 
not only when it is at a great distance from the needle. 
Otherwise there would be attraction as well as rotation. 




Fig. 138. 

Disc, Arago's A copper or other non-magnetic 

metallic disc, which, when rapidly rotated under a magnetic 
needle, supported independently of the disc, causes the 
needle to be deflected in the direction of rotation, and, when 
the velocity of the disc is sufficiently great, to rotate with it. 

Such a disc is shown in Fig. 138, at B. The movement of 
the needle is due to electric currents, induced by the disc 
moving through the field of the needle so as to cut its lines of 



190 



A DICTIONARY OF ELECTRICAL 



magnetic force. To obtain the best results the disc must move 
very rapidly, and should be near the needle. Moreover, the 
needle should be very powerful. 

This effect was discovered by Arago, in 1824. Since a mag- 
netic needle moving over a metallic plate produces electric 
currents in a direction which tend to stop the motion of the 
needle, a damping of the motion of a magnetic needle is some- 
times effected by causing it to move near a metal plate. 
The induced currents which the needle produces in the plate 
by its motion over it tend to retard the motions of the needle. 
(See Damping. Lenz's Lair.) 



Disc Armature.- 

tures.) 

Disc, Faraday's 




-(See Dynamo-Electric Machine, Arma- 



— A metallic disc movable in a 
magnetic field on an axis par- 
allel to the direction of the 
field. 

Such a disc is shown in Fig. 
139, and moves, as will be 
seen, so as to cut the lines 
of magnetic force at right 
angles. 



QS^ 



Fig. 139. 

The difference of potential generated by the motion of such 
a disc may be caused to produce a current, by providing a cir- 
cuit which is completed through the portion of the disc that at 
any moment of its rotation is situated between spring con- 
tacts resting on the axis of rotation and the circumference of 
the disc, respectively. 

In Barlow's, or Sturgeon's Wheel, Fig. 140, the wheel itself 
rotates in the direction shown, when a current is sent through 
it in a direction indicated by the arrows. 

Discharge. — The equalization of the difference of poten- 
tial between the terminals of a condenser or source, on their 
connection by a conductor, 



WORDS, TESMS AND PHRASES. 



191 




The removal of a charge from the surface of any charged 
conductor by connecting it with the earth, or another conduc- 
tor, effects its discharge. 

The discharge of an insulated conductor, a cloud, a con- 
denser, or a Leyden battery, is but momentary, and a cur- 
rent results which rap- 
idly passes from its max- 
imum value to zero. 

The discharge of a vol- 
taic battery, or a storage 
battery, is nearly contin- 
uous, and furnishes a 
current which is practi- &W- ll * - 

cally continuous, as distinguished from the momentary current 
produced by the discharge of a condenser. 

A discharge may be Conductive, Convective, or Disruptive. 

Discharge,. Conductive ■ — A discharge effected 

by leading the charge off through a conductor placed in con- 
tact with the charged body. 

Discharge, Convective The discharge which 

occurs from the points of a highly charged conductor, through 
the repulsion by the conductor of air particles that cany off 
minute charges therefrom. 

A convective discharge, though often attended by a feeble 
sound, is sometimes called a silent discharge in order to dis- 
tinguish it from the noisy, disruptive discharge, which is at- 
tended by a sharp snap, or, when considerable, by a loud 
report. 

A convective discharge is also called a glow or brush dis- 
charge. The latter is best seen at the small button at the 
end of the prime, or positive conductor, of a frictional electric 
machine. 

The positive discharge from a point or small rounded con- 
ductor is always brush shaped \ the negative discharge is al- 
ways star shaped. 



192 



A DICTIONARY OF ELECTRICAL 



In rarefied gases, the discharge is convective in character 
and produces various luminous effects of great beauty, the 
color of which depends on the kind of gas, and the size, shape, 
and material of electrodes, and on the degree of the vacuum. 
Thus, in the rarefied space of 
the vessel shown in Fig. 141, 
the discharge, becomes an ovoidal 
mass of light sometimes called the 
Philosopher's Egg. 

When the discharges in rarefied 
gases follow one another very rap- 
idly, alternations of light and dark- 
ness, or stratification, or strioz are 
produced. 

The breadth of the dark bands 
increases as the vacuum becomes 
higher. The light portions start 
at the positive electrode, and are 
hotter than the dark portions. 

The effects of the luminous con- 
vective discharge are best seen 
in exhausted glass tubes, called 
Geissler Tubes, containing residual 
atmospheres of various gases. (See 
Geissler Tubes.) 

Discharge, Disruptive The sudden, and 

more or less complete, discharge that takes place across an 
intervening non-conductor or dielectric. 

A mechanical strain of the dielectric occurs, which sudden- 
ly permits the discharge to pass as a spark, or rapid succes- 
sion of sparks. 

In air, the spark, when long, generally takes the zigzag 
path as shown in Fig. 142. 

These sparks consist of heated gases, and portions of the 
conductor that are volatilized by the heat. 




WORDS, TERMS AND PHRASES. 195 

The discharge of a Leyden jar or Condenser, may be dis- 
ruptive, as when the discharging rod is held with one knob con- 
nected with one coating, and the other near the other coating. 
It may be gradual, as when the two coatings are alternately 
connected with the ground. 

The stress is often sufficient to pierce the glass. 



Fig. Utf. 

Discharge, Duration of The time required 

to effect a complete disruptive discharge. 

The disruptive discharge is not instantaneous ; some time 
is required to effect it. Estimates of the duration of a flash of 
lightning, based on the duration of a Leyden jar discharge, are 
misleading from the enormous difference in the quantity and 
the potential in the two cases. 

Leyden jar discharges, are, however, accomplished in very 
small periods of time. 

Discharge Key.— (See Key, Discharge.) 

Discharge, Lateral (See Lateral Discharge.) 

Discharge, Oscillating A number of suc- 
cessive discharges and recharges which occur on the disruptive 
discharge of a Leyden jar, or condenser. 

The disruptive discharge of a Leyden jar, or condenser, is 
not effected by a single rush of electricity. When discharged 
through a small resistance, a number of alternate partial dis- 



194 A DICTIONARY OF ELECTRICAL 

charges and recharges occur, which produce true oscillations 
or undulatory discharges. 

These oscillations are caused by the induction of the dis- 
charge on itself, and are similar to the mutual induction of a 
current. 

Discharger, Universal (See Universal Dis- 
charger.) 

Discharging Rod or Tongs.— Metallic rods terminated 
at one end with balls and connected at the other by a 
swinging joint, and capable of mo- 
tion at the free ends towards, or from, 
one another; employed for the dis- 
charge of Leyden batteries or con- 
densers. 

The insulated handles H, H, Fig. 143, 
permit the balls at M M to be readily 
applied to the opposite coatings of the 
jar or condenser. 
Disconnections. — A term em- 
Fig. Ik3. ployed to designate one of the varieties 

of faults caused by the accidental breaking or disconnection 
of a circuit. 
Disconnections of this kind may be : 

(1) Total; as by a switch inadvertently left open ; or by the 
accidental breaking of a part of the circuit. 

(2) Partial; as by a dirty contact; a loose, or badly soldered 
joint ; a poorly clamped binding screw ; a loose terminal, or a 
bad earth. 

(3) Intermittent ; as by swinging joints; alternate expansions 
or contractions, on changes of temperature; the collection of 
dust and dirt in dry weather, and their washing out in wet 
weather. 

Dispersion Photometer.— (See Photometer, Disper- 
sion.) 




WORDS, TERMS AND PHRASES. 195 

Dissimulated or Latent Electricity.— The condition 
of an electric charge when placed near an opposite charge, as 
in a Leyden jar or condenser. 

In this case, merely touching one of these charged surfaces 
will not effect its complete discharge. (See Bound and Free 
Charge.) 

Electricity in the condition of a bound charge was formerly 
called latent electricity. This term is now in disuse. 

Dissipation of Charge. — The gradual but final loss of 
any charge by leakage, which occurs even in a well insulated 
conductor. 

This loss is more rapid with negatively charged conductors, 
than with those positively charged. 

Crookcs, of England, has retained a charge in conductors for 
years, without appreciable leakage, by placing the conductors 
in vessels in which a high vacuum was maintained. (See 
Vacuum, High.) 

Dissociation. — The separation of a chemica compound 
into its elementary parts by the action of heat. 

Distillation, Dry or Destructive The 

action of heat on an organic substance, while out of contact 
with air, as a result of which the substance is decomposed into 
simpler and more stable compounds. 

The products resulting from the decomposition may be suc- 
cessively collected by the ordinary processes of distillation. 

Distillation, Electric The distillation of 

a liquid in which the effects of heat are aided by an electrifica- 
tion of the liquid. 

Beccaria discovered that an electrified liquid evaporates 
more rapidly than when unelectrified. 

Distribution Box. — (See Box, Distribution.) 

Distribution of Electric Charge. (See Charge, Dis- 
tribution of.) 



196 A DICTIONARY OF ELECTRICAL 

Distribution of Electricity, Systems of.— (See Sys- 
tems of Distribution by Alternating Currents; — by Direct 
Currents.) 

Door-Opener, Electric A device for open- 
ing a door from a distance by electricity. 

Various devices consisting of electro-magnets, acting against, 
or controlling, springs or weights, are employed for this 
purpose. 

Double-Carbon Arc Lamp.-An electric arc lamp 
provided with two pairs of carbon electrodes, so arranged, 
that when one pair is consumed, the circuit is automatically 
completed through the other pair. 

Double-Contact Key.— (See Key, Double- Contact.) 

Double-Current, or Reverse Current Working. 

— The employment, in systems of telegraphy, by means of 
suitable keys, of currents from voltaic batteries, in alternately 
opposite directions thus increasing the speed of signaling. 

Double -Fluid Electrical Hypothesis. — (See Elec- 
tricity, Hypothesis of.) 

Double-Fluid Voltaic Cells.— (See Voltaic Cells.) 

Double-Refraction. — (See Refraction, Double.) 

Double-Refraction, Electric (See Electric, 

Double Refraction.) 

Double-Touch, Magnetization by A 

method for producing magnetization by the simultaneous 
touch of two magnet poles. (See Magnetization, Methods of. ) 

Doubler of Electricity. — An early form of continuous 
elctrophorus. (See Electrophorus.) 

Drill, Electro-Magnetic A drill, applied 

especially to blasting or mining operations, operated by 
means of electricity. 

Drum, Electro-Magnetic A drum, used in feats 

of legerdemain, operated by an automatic electro-magnetic 
make and break apparatus. 



W6RDS, TERMS AND PHRASES. 197 

Brum or Cylinder Armature. — An armature for a 
dynamo-electric machine, in which the coils are wrapped 
around the outside of a hollow cylindrical or drum-shaped 
core. (See Dynamo-Electric Machine, Armatures of.) 

Dry Pile. — A voltaic pile or battery consisting of numerous 
cells, the voltaic couple in each of which consists of sheets of 
paper covered with zinc-foil on one side, and black oxide of 
manganese on the other. 

Various modifications of the above are possible. 

Duplex Telegraphy. — Devices by means of which two 
messages can be simultaneously sent over a single wire, in 
opposite directions. (See Telegraphy, Duplex.) 

Duration of Electric Discharge. — (See Discharge, 
Duration of.) 

Dyad. — A dyad or bivalent element, is one which has two 
bonds by which it can unite or combine with another element. 

An element whose atomicity is bivalent. 

Dyeing, Electric The application of electricity 

to the reduction, or the oxidation, of the aniline salts used in 
dyeing. 

Goppelsroder, in his processes of electro-dyeing, forms and 
fixes aniline black on cloths as follows; viz., the cloth, satu- 
rated with aniline salt, is placed on an insulated metallic 
plate, inert to the aniline salt, and connected with one pole 
of a battery or other electric source. The other pole is con- 
nected with a metallic plate on which the required design is 
drawn. On the passage of the current, the design is traced in 
aniline black on the cloth. A minute or two suffices for the 
operation. 

A species of electrolytic writing is obtained on cloths ar- 
ranged as above by substituting a carbon pencil for the metallic 
plate. On writing with this pencil, as with an ordinary pencil, 
the passage of the current so directed, is followed by the de- 
position of aniline black. 



198 A DICTIONARY OF ELECTRICAL 

By means of a somewhat similar process writing in white 
on a colored ground is obtained. 
Dynamic Attraction.— (See Attraction, Dynamic.) 
Dynamic Electricity. — A term formerly employed for 
current electricity. Now going out of use. 

Dynamics, Electro (See Electro Dynamics.) 

Dynamo Battery.— (See Battery, Dynamo. ) 
Dynamo-Electric Machine.— A machine for the con- 
version of mechanical energy into electrical energy, by means 
of electro-magnetic induction. 

The term is also applied to a machine by means of which 
electrical energy is converted into mechanical energy by means 
of electro-magnetic induction. Machines of the latter class, 
are generally called motors, those of the former, generators. 

A dynamo-electric generator, or a dynamo-electric machine 
proper, consists of the following parts, viz. : 

(1) The revolving portion, usually the Armaturejin which the 
electro-motive force is developed, which produces the current. 

It must be borne in mind that it is not current but differ- 
ences of electric potential, or electro-motive forces, that are de- 
veloped by any electric source from which a current is obtained. 
For ease of reference, however, we will speak of an electric cur- 
rent as being generated by the armature, or source. No ambig- 
uity will be introduced if the student bears the above in mind. 

(2) The Field Magnets, which produce the field in which the 
armature revolves. 

(3) The Pole Pieces, or free terminals of the field magnets. 

(4) The Commutator, by which the currents developed in the 
armature are caused to flow in one and the same direction. In 
alternating machines and some continuous current dynamos 
this part is called the Collector. 

(5) The Collecting Brushes, that rest on the Commutator 
Cylinder and take off the current generated in the armature. 

Dynamo-Electric Machine, Armature. — The coils 
of insulated wire and the iron core on or around which the coils 
are wound. 



WORDS, TERMS AND PHRASES. 



199 




Armatures are generally divided into the following- classes, 
viz. : 

(1) Ring- Armatures, in which the armature coils are wound 
around a ring shaped core, as shown in Fig. 144. 

(2) Drum- A r m a- 
tures, in which the 
armature coils are 
w o u n d longitudi- 
nally over the sur- 
face of a cylinder or 
drum, as shown in 
Fig. 145. 

(3) Pole or Radial- 
Armatures, in which ^- lltlu 

the armature coils are wound on separate poles that project 

radially from the periphery of a disc, as shown in Fig. 146. 

(4) Disc Armatures, 
in which flat coils are 
supported on the sur- 
face of a disc. 

Dynamos are some- 
times divided into Uni- 
polar, Bipolar and Mul- 
ti polar. A unipolar- 
armature is one whose 
polarity is never re- 
versed. A bipolar- 
ar mature is one in 
which the polarity is 
Fig. ii*5. reversed twice in every 

rotation ; multipolar-armatures have their polarity reversed a 

number of times in every rotation. 

Dynamo-Electric machine, Armature Coils.— The 
coils, strips or bars that are wound on the armature core. 
To avoid needless resistance the wire should be as short 




200 A DICTIONARY OF ELECTRICAL 

and thick as will enable the desired current to be obtained 
without excessive speed of rotation. 

The armature coils should enclose as many lines of force as 
possible (1 e., they should have as nearly a circular outline as 
possible). In drum-armatures, the breadth should nearly equal 
the length, unless other considerations prevent. 




When the armature wire consists of rods or bars, it should 
be laminated or slit in planes perpendicular to the lines of 
force so as to avoid eddy currents. The greater the number 
of coils, other things being equal, the more uniform the cur- 
rent generated. The separate coils should be symmetrically 
disposed, otherwise irregular induction, and consequent spark- 
ing at the commutator results. 

The coils of pole-armatures should be wound near the poles 
rather than on the middle of the cores; In order to avoid undue 
heating, spaces for air ventilation are not inadvisable. Vari- 
ous connections of the armature coils are used. 

In some machines all the coils are connected in a closed cir- 
cuit. In some, the coils are independent of one another, and, 
either for the entire revolution, or for a part of a revolution, 
are on an open circuit. 

In alternating current dynamos in order to obtain the rapid 
reversals or alternations of current, whieh in some machines 



WORDS, TERMS AND PHRASES. 



201 



are as high at 12,000 per minute, a number of poles of alternate 
polarity are employed. The separate coils that are used on 
the armature may be coupled either in series or in mul- 
tiple-arc. 

Where a comparatively 
low electro-motive force is 
sufficient, such as for incan- 
descent lamps in multiple- 
arc, the separate coils are 
united In parallel; but for 
purposes where a consider- 
able electro-motive force is 
necessary, as, for example, 
in systems of alternate cur- 
rent distribution, with con- 
verters at considerable dis- 
tances from the generating, 
alternating current dynamo, the\ 
series, as shown in the Fisr. 147. 




Fig. 147. 

often connected in 



Dynamo-Electric machine, Armature Core.— 

The iron core, on, or around which, the armature coils are 
wound. 

The armature core is laminated for the purpose of avoiding 
the formation of eddy currents. 

In drum, and in ring-armatures, the laminae should be in the 
form of thin insulated discs or plates of soft iron ; in pole-arma- 
tures they should be in the form of bundles of insulated wires. 

The iron in the cores should be of such an area of cross 
section, as not to be readily oversaturated. 

Dynamo-Electric machine, Cause of Current 
generated by The current developed in the arma- 
ture coils is due to the cutting of the lines of magnetic force 
of the field by the coils during the rotation of the armature. 

If a loop of wire, whose ends are connected to the two-part 



202 



A DICTIONARY OF ELECTRICAL 




commutator, shown in Fig. 148, be rotated in the magnetic 
field between the magnet poles N and S, in the direction of the 
» large arrow, cur- 

rents will be gen- 
erated which will 
flow in the direc- 
o tion indicated by 
the small arrows 
during its motion 
past the, north 
Fig. IIS. pole from the top 

to the bottom, but in the opposite direction during its motion 
past the south pole, from the bottom to the top. If now the 
brushes rest on the com- 
mutator in the position 
shown in the Fig. 149, the 
vertical line of the gap 
between the poles corre- 
sponding with the vertical 
gap between the commu- 
tator segments, the cur- 
rents generated in the loop 
will be caused to flow in one and the same direction, and 
B' will become the positive brush since the end of the 

loop is connected wit}* it 
only so long as it is posi- 
tive. As soon as it becomes 
negative, from the current 
in the loop flowing in the 
opposite direction, the 
other end, which is then 
positive, is connected with 
the positive brush. 
Fig. 150. A similar series of 

changes occur at the negative brush, B. 
Theoretically, the neutral points, where the brushes rest, 





WORDS, TERMS AND PHRASES. 



203 



would be in the vertical line coinciding with that of the gap 
between the poles. An inspection of the figure shows that 
the Neutral Line, or the Diameter of Commutation, is dis- 
placed in the direction of rotation. (See Diameter of Com- 
mutation). The displacement of the brushes, so necessitated, 
is called the lead. The cause of the lead is the reaction that 
occurs between the magnetic poles of the field magnets and 
those of the armature, the result of which is to displace the 
field magnet poles, and to cause a change in the density in the 
field. This is shown in Fig. 150, where the density of the lines 
of force indicates the position of the diameter of commutation 
as being near n s, or at right angles to the diameter of greatest 
average magnetic density. The magnetic lag also influences 
the positive of the neutral line. (See Lead. Angle of Lag.) 

Dynamo-Electric machine, Collecting Brushes. 
— Metallic brushes which bear on the commutator cylinder, 
and take off the current generated by the difference of poten- 
tial in the armature coils. (See Brushes, Collecting.) 

Dynamo-Electric Machine, Commutator. — The 
part of a dynamo-electric machine which is designed to cause 
the alternating currents produced in the armature to flow in 
one and the same direction in the external circuit. 





Fig. 151. Fig. 152. 

The character of the commutator depends on the shape, 
arrangement, and number of armature coils, and on the 
character of the magnetic field. 



204 



A DICTIONARY OF ELECTRICAL 



In action, the commutator is subject to wear from the friction 
of the brushes, and the burning action of destructive sparks. 
The commutator segments are, therefore, made of compara- 
tively thick pieces of metal, insulated from one another, and 
supported on a commutator cylinder usually placed on the 
shaft of the armature. 

The enJs of the armature coils are connected to commuta- 
tor strips or segments. 





Fig. 153. 

Figs. 151, 152, and 153, show the connections of an arma- 
ture coil to the plates of a two-part commutator. (See Com- 
mutator.) 

The connections of a four-part commutator for a ring arma- 
ture, and the connections of the coils are shown in the an- 
nexed Fig. 154. 

The commutator strips may either connect the separate 
coils in one closed circuit, in which the coils are all connected 
with one another, or, in an open circuited armature, the 
separate coils are independent of one another. 

Dynamo-Electric Machine, Field Hagnet§.— The 
electro magnets employed to produce the magnetic field of a 
dynamo-electric machine. 



WORDS, TERM S AND PHRASES. 



205 



The field magnets consist of a suitable frame, or core, on 
which the field magnet coils are wound. 

The field magnet cores are made of thick and solid iron, as 
soft as possible. They should contain plenty of iron in order 
to avoid too ready magnetic saturation. 

All edges and corners are to be avoided, since they tend to 
cause an irregular distribution of the field. 




R R R 
Fig. 155. 



R R R 

Fig. 156. 



The field magnets should have sufficient magnetic strength 
to prevent the magnetizing effect of the armature from 
unduly influencing the field, and thus, by causing too great a 
lead, produce injurious sparking. 

Dynamo-Electric Machine, Methods of Increas- 
ing the Electro-Motive Force generated by 

The electro-motive force of a dynamo-electric machine may 
be increased in the following ways, viz. : 



206 



A DICTIONARY OF ELECTRICAL 



(1) By increasing- its Speed of Rotation. 

(2) By increasing the Strength of the Magnetic Field be- 
tween which the armature rotates. 

(3) By increasing* the Size of the Field through which the 
armature passes in unit time, the intensity remaining the same. 

(4) By increasing* the Number of Armature Windings, i. e., 
by making successive parts of the same wire pass simultane- 
ously through the field. 

(5) By increasing the Number of Fields passed through by 
the same wire. 

Dynamo-Electric Machine, Pole Pieces.— Massive 

pieces of iron placed on 
the poles of the field mag- 
nets of dynamo-electric 
machines, to define and 
limit the magnetic field. 
The pole pieces should 
be of massive, soft iron. 
They are sometimes 
laminated so as to avoid 
eddy currents. When de- 
signed to produce a uni- 
form field they must ex- 
tend on each side of the 
armature, but not too far, 
else a loss will be occa- 
sioned by the lines of 
magnetic force closing 
directly through the 
edges of the opposite pole 




R 

Fig. 157. 

pieces, instead of through the armature. 
Dynamo-Electric Machines, Compound Wound 

Machines whose field magnets are excited by more 

than one circuit of coils, or by more than a single electric 
source. 

Compound dynamos are of two classes, viz. : 



WORDS. TERMS AND PHRASES. 



207 



(1) Those designed to produce a Constant Potential, and 

(2) Those designed to produce a Constant Current. 
For Constant Potential. 

The combination of a Series and Separately Excited ma- 



The field is in series with the 
additional and separate excita- 



chine is shown in Fig. 155. 
armature, but has also an 
tion. 

The combination of a 
Series and Shunt machine 
ensures the excitation of 
the field both by the main 
and by a shunted current. 
Such a combination is 
shown in Fig. 156. 

For Constant Current. 

The combination of 
shunt and separately ex- 
cited machine is shown in 
Fig. 157. In this machine 
the field is excited by 
means of a shunt to the 
external circuit, and by a 
current produced by a sep- 
arate source. 

The combination of a 
Series and Magneto Ma- 
chine is shown in Fig. 151 
constant current. 

Dynamo-Electric Machines, Varieties of 

Dynamo-electric machines may be divided into different 
classes according to the manner in which their field mag- 
nets are excited. 

In a Series Dynamo, Fig. 159, the armature circuit is con- 
nected in series with the field circuit; therefore the entire arm- 
ature current must pass through the field coils. 




it -^'-o^'-i- 4'<- S&, ilH^ 4M. -'"<r I 

Fig. 158. 
This, also, is designed to give a 



208 A DICTIONARY OF ELECTRICAL 

In a Shunt Dynamo, Fig. 160, the field magnet coils are 
placed in a shunt to the external circuit, so that only a por- 
tion of the current generated in the armature passes through 
the field magnet coils, but all the difference of potential of the 
armature acts at the terminals of the field circuit. 

In a Separately Excited Dynamo, Fig. 161, the field magnet 
coils have no connection with the armature coils, but receive 
then- current from a'separate machine or source. 





D D D D 
Fig. 159. 






D D D D 
Fig. 160. 



The Magneto-Electric machine, Fig. 162, has no field magnet 
coils, its field being due to permanent steel magnets. 

The author has collated the above on dynamo-electric 
machines largely from S. P. Thompson's admirable book on 
" Djmamo-Electric Machinery," third edition, to which the stu- 
dent is referred for further particulars of construction or 



WORDS, TERMS AND PHRASES. 



209 



operation. He is also indebted to Hering's "Principles of 
Dynamo-Electric Machines." 

Dynamograpli.— A term sometimes applied to a type- 
writing telegraph that records the message in type-written 
characters, both at the sending and the receiving ends. 

Dynamometer.— A name 
given to a variety of appara- 
tus for measuring the power 
of an engine or motor. 

In all dynamometers, the 
stress on the belt, or other 
moving part, is measured, say 
in pounds, and the speed of 
the moving part is also meas- 
ured in feet per second. The 
product of the strain in pounds 
by the velocity in feet per 
second, divided by 550, will 
give the horse power. 

One of the many forms of 
dynamometers is shown in 
Fig. 163. It is known as Par- 
sons' Dynamometer. Fig. 161. 

The driving pulleyls shown at A, and the driven pulley at 
C. Weights hung at Q are varied so as to maintain the axes 
of the suspended pulleys, D and B, as nearly as possible at the 
same height. Then the tension T 1 and T 2 , of the sides O and 
O', of the belts, will be represented by the following equation : 
P-Q 




l & H. ,y'^ *yfe 



T 2 -T x 



-, from which, knowing the belt speed, the 



horse power may be deduced. 

Dynamometer, Eleetro 

ometer for the measurement of electric currents. 



-A form of galvan- 



210 



A DICTIONARY OF ELECTRICAL 



In Siemens' Electro Dynamometer, shown in Fig. 164, 
there are two coils ; a fixed coil C, secured to an upright sup- 
port, and a movable coil D , consisting- often of but a single turn 
of wire. The movable coil is suspended by means of a thread 
and a delicate spring S, capable of being twisted by turning 
a milled screw-head through an angle of torsion measured 
on a scale by means of an index connected to the screw-head. 
The two ends of the movable coil dip into mercury cups so 
connected that the current to be measured passes through the 
fixed and movable coils in series. 

When ready for use, the movable 
coil is at right angles to the fixed coil. 
The current to be measured is then 
sent into the coils, and their mutual 
action tends to place the movable coil 
parallel to the fixed coil against the 
torsion of the spring S. The amount 
of this force can be ascertained by de- 
termining the amount of torsion re- 
quired to bring the movable coil back 
to its zero position. 

Since the same current passes through 
both the fixed and movable coils, and 
they both act on each other, the deflect- 
ing force here is evidently proportional to the square of the 
strength of the current to be measured. The deflecting force, 
and consequently the current strength, is therefore propor- 
tional to the square root of the angle of torsion, and not di- 
rectly to the angle of torsion. 

Dyne. — The unit of force. 

The force which in one second can impart a velocity of one 
centimetre per second to a mass of one gramme. 




Fig. 162. 



Earth Circuit 

Qrounded.) 



or Ground Circuit.— (See Circuity 



WORDS, TERMS AND PHRASES. 



211 



Earth Currents. — Electric currents flowing through 
different parts of the earth caused by a difference of potential 
at different parts. 

The causes of these differences of potential are various. 

Earth, Dead or Solid 

— (See Earths.) 

Earth or Ground. — The earth 
or ground which forms part of an 
electric circuit. 

A circuit is put to earth or ground 
when the earth is used for a portion 
of the circuit. 

The resistance of an earth con- 
nection may vary in time from the 
following causes, xiz. : 

(1) The corrosion of the plate. 
This is especially apt to occur in 
the case of a copper plate. 

(2) From polarization, a counter 
electro-motive force being produced, 
thus introducing a spurious resist- 
ance. (See Spurious Resistance.) 

Earth, Partial (See 

Earths.) 

Earth, Swinging (See 

Earths.) 

Earths. — Faults in telegraph or 
other lines caused by accidental con- 
tact of line with the ground or 
earth. 

Earths are of three kinds, viz. : 

(1) Total, or Dead Earth, where the 
grounded or connected with the earth. 

(2) Partial Earth, or where the wire is in imperfect con- 
nection with the earth, 




Fig. 163. 
wire is thoroughly 



212 



A DICTIONARY OF ELECTRICAL 



(3) Intermittent Earth, or when the wire makes intermittent 
contact with the earth by the action of the wind, or by- 
occasional expansion by heat. 

Ebonite or Vulcanite.— A black variety of hard rubber 
which possesses high powers of insulation and specific induc- 
tive capacity. 




Vulcanite rubbed with cat-skin acts as one of the best known 
substances for becoming electrified by friction. For this pur- 
pose it should be thoroughly dried, 



WORDS, TERMS AND PHRASES. 



213 



Economic Coefficient, or Efficiency of a Dynamo. 

— (See Coefficient, Economic, of a Dynamo.) 

Effect, Edison An electric discharge between 

one of the terminals of the incandescent filament of the elec- 
tric lamp, and a metallic plate placed near the filament but 
disconnected therefrom, as soon as a certain difference of po- 
tential is reached between the lamp terminals. 

The effect of the discharge is to produce a current in a 
circuit connected to one pole of the lamp terminals and the 
metallic plate, as may be 
shown by means of a gal- 
vanometer. 



Effect, Hall 



— An effect produced by 
placing a very thin me- 
tallic strip, conveying an 
electric current, in a 
strong magnetic field. 

The cross A B C D, Fig. 
IGo, is cut out of a gold 
leaf or other very thin 
metallic sheet. The ends 
A and B are connected 
with the terminals of a 
battery S, and C and D 
with the galvanometer G. 




Fig. 165. 



None of the battery current can therefore flow through the 
alvanometer. 

If, now, the metallic cross be placed in a powerful magnetic 
field, the lines of force of which are perpendicular to the plane 
of the cross, the deflection of the galvanometer needle will 
show the existence of a current, which, if the battery current 
flows in the direction of the arrow, or from A to B, if the lines 
of magnetic force pass through the leaf from the front to the 
back of the sheet, when the cross is formed of gold, silver, 



214 A DICTIONARY OE ELECTRICAL 

platinum or tin-foil, will flow through C D, from C to D, but in 
the opposite direction if formed of iron. These effects cease 
if the conductor is increased in thickness beyond a certain 
extent. 

Effect, Joule A term applied to the heat de- 
veloped in a conductor by the passage through it of an elec- 
tric current. 

The rate at which this occurs is proportional to the resist- 
ance of the conductor multiplied by the square of the current. 
(See Heat, Electric.) 

Effect, Peltier The heating effect produced by 

the passage of an electric current across a thermo-electric junc- 
tion. (See Junction, T her mo-Electric.) 

The passage of the current across a thermo-electric junction 
produces either heat, or cold. If heat is produced by its 
passage in one direction, cold is produced by its passage in the 
opposite direction. The Peltier effect may, therefore, mask 
the Joule effect. 

The Peltier effect is therefore the converse of the thermo- 
electro effect, where the uneqal heating of metallic junctions 
produces an electric current. (See Effect, Joule ; Effect, 
Thomson. ) 

The quantity of heat absorbed or emitted by the Peltier 
effect is proportional to the current strength, and not, as in 
the Joule effect, to the square of the current. 

Effect, Photo- Voltaic (See Photo-Voltaic 

Effect. Selenium Cell.) 

Effect, Thomson A term applied to the increase 

or decrease in the differences of temperature is an unequally 
heated conductor, produced by the passage of an electrical 
current through the conductor. 

The effects vary according to whether the current passes 
from a colder to a hotter part of the wire, or the reverse. 

These effects differ in direction in different metals, and 



WORDS, TERMS AND PHRASES. 215 

are absent in lead. Thomson has pointed out the similarity 
between this species of thermo-electric phenomena, and 
convection by heat, or the phenomena of a liquid circulating 
in a closed rectangular tube, under the influence of difference 
of temperature, in which the heated fluid gives out heat in the 
cooler parts of the circuit, and takes in heat in the warmer 
parts. This would presuppose that positive electricity carries 
heat in copper like a real fluid, but that in iron it acts as though 
its specific heat were a negative quantity, in which respect it 
is unlike a true fluid. 

" We may express" says Maxwell "both the Peltier and the 
Thomson effects by stating that when an electric current is 
flowing from places of smaller to places of greater thermo- 
electric power, heat is absorbed, and when it is flowing in the 
reverse direction heat is generated, and this whether the dif- 
ference of thermo-electric power in the two places arises from 
a difference in the nature of the metal, or from a difference of 
temperature in the same metal." 

Efficiency of Conversion of Dynamo The 

total electric energy developed by a dynamo, divided by 
the total mechanical energy required to drive the dynamo. 
(See Coefficient, Economic, of Dynamo.) 

Efficiency of Dynamo. — (See Coefficient, Economic of 
Dynamo.) 

Efflorescence. — The crystallization of a salt, above the 
line of liquid, on the surface of a vessel containing a saline 
solution. 

The liquid, by capillarity in a porous vessel, or by adhe- 
sion in an impervious vessel, rises above the level of the main 
liquid line and, evaporating, deposits crystals on the vessel. 

This process is technically called creeping, and is often the 
cause of much annoyance in voltaic cells. 

Egg, Philosopher's (See Discharge, Convective.) 

Electric Absorption.— (See Absorption, Electric.) 



216 A DICTIONARY OF ELECTRICAL 

Electric Alarm.— (See Alarm, Electric.) 
Electric Amalgam.— (See Amalgam, Electric.) 
Electric Analysis. — (See Analysis, Electric.) 
Electric Annealing.— A process for annealing metals, 
in which electric heating is substituted for ordinary heating. 
Electric Battery. — (See Battery, Electric.) 
Electric Blasting. — (See Blasting, Electric.) 
Electric Bleaching.— (See Bleaching, Electric.) 
Electric Blow-Pipe.— (See Blow-Pipe. Electric.) 
Electric Boat. — (See Boat, Electric.) 
Electric Bobbin.— (See Bobbin, Electric.) 
Electric Body Protector. — (See Body Protector, 
Electric.) 
Electric Boiler Feed.— (See Boiler Feed, Electric.) 
Electric Bridge.— (See Bridge, Electric.) 
Electric Buoy. — (See Buoy, Electric.) 
Electric Burner. — (See Burner, Electric.) 
Electric Buzzer. — (See Buzzer, Electric.) 
Electric Calorimeter. — (See Calorimeter, Electric.) 
Electric Cautery.— (See Cautery, Electric.) 
Electric Charge.— (See Charge, Electric.) 
Electric Chimes.— (See Chimes, Electric.) 
Electric Chronograph.— (See Chronograph, Electric.) 
Electric Chronoscope. — (See Chronoscope, Electric.) 
Electric Clepsydra.— (See Clepsydra, Electric.) 
Electric Clock. — (See Clock, Electric.) 
Electric Coil. — (See Coil, Electric.) 
Electric Column. — (See Column, Electric.) 
Electrically Controlled Clock.— (See Clock, Con- 
trolled.) 



WORDS, TERMS AND PHRASES. 217 

Electric Controlling Clock.— (See Clock, Controlling.) 

Electric Convection of Heat.— (See Convection of 
Heat, Electric.) 
Electric Cords.— (See Cords, Electric.) 
Electric Counter. — (See Counter, Electric.) 
Electric Cross.— (See Cross, Electric.) 
Electric Crucible.— (See Crucible, Electric.) 
Electric Current. — (See Current, Electric.) 
Electric Decomposition.— (See Decomposition, Elec- 
tric.) 

Electric Deposition. — (See Deposition, Electric.) 
Electric Distillation.— (See Distillation, Electric.) 

Electric Double Refraction.— The transient or mo- 
mentary power of double refraction, ac- 
quired by a transparent substance when 
placed in an electric field. (See Refrac- 
tion, Double.) 

The intensity of the double refraction is 
proportional to the square of the electric 
force. 

This action is due to the strain caused 
by the electrostatic stress produced by the 
field. A similar transient power of double 
refraction is acquired by many transparent 
bodies when subjected to simple mechan- 
ical stress. 

Electric Dyeing.— (See Dyeing, 
Electric.) 

Electric Dynamometer, Siemens'. 

— (See Dynamometer, Electro.) Fig7i66. 

Electric Eel (Gymnotus electricus.)— An eel possessing 
the power of giving powerful electric shocks. 




Si§ A DICTIONARY OF ELECTRICAL 

The electricity is produced by an organ extending the entire 
length of the body. 

According to Faraday, the shock given by a specimen of the 
animal examined by him was equal to that of 15 Leyden jars, 
having a total surface of 25 square feet. Fig. 166 shows the 
general appearance of the animal. 

Electric Energy.— (See Energy, Electric.) 

Electric Entropy.— (See Entropy, Electric.) 

Electric Escape.— (See Escape, Electric.) 

Electric Etching.— (See Etching, Electric.) 

Electric Excitability of Xerve Fibre.— (See Excita- 
bility of Nerve Fibre.) 

Electric Expansion.— (See Expansion, Electric.) 

Electric Explorer.— (See Explorer, Electric.) 

Electric Field. — A field of force, traversed by imagin 

ary lines of force somewhat similar to the magnetic field. 

(See Field, Electric.) 
Electric Figures, Breath.— (See Figures, Electric, 

Breath.) 

Electric Figures, Lichtenberg's.— (See Figures, Elec- 
tric, Lichtenberg's.) 

Electric Fishes.— (See Fishes, Electric.) 
Electric Flyer, or Fly.— (See Flyer, Electric.) 
Electric Fog.— (See Fog, Electric.) 

Electric Force. — The force developed by electricity. 
This term is generally limited to the force of attraction or 
repulsion produced by an electrostatic charge. 

Electric Furnace. — (See Furnace, Electric.) 
Electric Fuse. — (See Fuse, Electric.) 
Electric Gas Lighting.— (See Gas Lighting, Electric.) 
Electric Gilding.— (See Gilding, Electric.) 



\VORDS, TERMS AND PHRASES. 2l§ 

Electric Oovernor. — (See Governor, Electric.) 

Electric Head Eight.— (See Head Light, Electric.) 

Electric Heat. — (See Heat, Electric.) 

Electric Heater.— (See Heater, Electric.) 

Electric Horse Power.— (See Horse Power, Electric.) 

Electric Hydrotasimeter. — (See Hydrotasimeter, Elec- 
tric.) 
Electric Ignition. — (See Ignition, Electric.) 
Electric Images.— (See Images, Electric.) 
Electric Incandescence.— (See Incandescence, Elec- 
tric.) 
Electric Indicators.— (See Indicators, Electric.) 
Electric Insolation.— (See Sunstroke, Electric.) 
Electric Jewelry. — (See Jewelry, Electric.) 
Electric Lamp, Arc. — (See Lamp, Electric, Arc.) 
Electric Lamp, Incandescent.— (See Lamp, Incan- 
descent.) 

Electric Lamp, Semi-Incandescent.— (See Lamp, 
Semi-Incandescent. ) 
Electric Letter-Box.— (See Letter-Box, Electric.) 
Electric Locomotive.— (See Locomotive, Electric.) 
Electric Log.— (See Log, Electric.) 
Electric Loop.— (See Loop, Electric.) 

Electric machines, Electrostatic Induction 

— (See Machines, Electrostatic Induction.) 

Electric Machines, Frictional — (See achin 

Electric, Frictional.) 
Electric Mains.— (See Mains, Electric.) 
Electric Masses.— (See Masses, Electric.) 
Electric Measurement.— (See Measurement, Electric.) 



220 A DICTIONARY OP ELECTRICAL 

Electric Meter.— (See Meter, Electric.) 
Electric Mine Exploder.— (See Fuse, Electric.) 
Electric Motor.— (See Motor, Electric.) 
Electric Musket.— (See Musket, Electric.) 
Electric Organ. — (See Organ, Electric.) 
Electric Oscillations. — (See Oscillations, Electric.) 
Electric Osmose.— (See Osmose, Electric.) 
Electric Pen. — (See Pen, Electric.) 
Electric Pendulum.— (See Pendulum, Electric.) 

Electric Phosphorescence. — (See Phosphorescence, 
Electric.) 
Electric Piano.— (See Piano, Electric.) 
Electric Plough.— (See Plough, Electric.) 
Electric Potential. — (See Potential, Electric.) 
Electric Probe.— (See Probe, Electric.) 
Electric Prostration.— (See Sunstroke, Electric.) 
Electric Protection. — (See Lightning Rods.) 

Electric Protection of Metals.— (See Metals, Elec- 
tric Protection.) 

Electric Pyrometer.- 1 - (See Pyrometer, Electric.) 

Electric Ray (Raia torpedo). — A species of fish named 
the ray, which, like the electric eel, possesses the power of 
producing electricity. 

The electric organ is situated at the back of the head, and 
consists of hundreds of polygonal, cellular laminae, supplied 
with numerous nerve fibres, as shown in Fig. 167. 

Electric Rectification of Alcohol.— (See Alcohol, 
Electric Rectification of.) 

Electric Register, Watchman's (See Watch- 
man's Electric Register.) 



WORDS, TERMS AND PHRASES. 



221 



Electric Registering Apparatus.— (See Registering 
Apparatus, Electric.) 
Electric Resistance.— (See Resistance, Electric.) 
Electric Safety Lamp- (See Safety Lamp, Electric.) 
Electric Seismograph.— (See Seismograph, Electric.) 

Electric Sh a d o w. — (See 
Shadow, Electric.) 

Electric Shock.— (See Shock, 
Electric.) 

Electric Socket for Lamp, 

— (See Socket, Electric Lamp.) 

Electric Soldering.— (See Sol- 
dering, Elective.) 

Electric Storms. — (See Storms, 
Electric.) 

Electric Striae.— (See S trice, 
Electric.) 

Electric Sunstroke. — (See 

Sunstroke, Electric.) 

Electric Target. —(See Target, 
Electric.) 

Electric Teazer.— (See Teaz- 
er, Electric Current.) 

Electric Tempering.— A pro- 
cess for tempering metals in which 
heat of electric origin is employed 
instead of ordinary furnace heat. (See Tempering, Electric.) 
Electric Tension.— (See Tension, Electric.) 
Electric Thermometer.— (See Thermometer, Electric.) 
Electric Time-Ball.— (See Time-Ball, Electric.) 
Electric Torpedo.— (See Torpedo, Electric.) 




Fig. 167. 



222 A DICTIONARY OF ELECTRICAL 

Electric Tower.— (See Tower, Electric) 
Electric Transmitters.— (See Transmitters, Electric.) 
Electric Typewriter.— (See Typewriter, Electric.) 
Electric Valve.— (See Valve, Electric.) 
Electric Varnish.— (See Varnish, Electric.) 
Electric Welding.— (See Welding, Electric.) 
Electric Whirl.— (See Whirl, Electric.) 
Electric Whistle.— (See Whistle, Steam, Electric.) 
Electric Work.— (See Work, Electric.) 
Electrical Convection of Heat.— A term employed 
to express the dissymmetrical distribution of temperature 
that occurs when a current of electricity is sent through a 
metallic wire, the middle of which is maintained at a con- 
stant temperature, and the ends at the temperature of melt- 
ing- ice. 
Electrical Death.— (See Death, Electrical.) 
Electricity. — The name given to the unknown thing, 
matter, or force, or both, which is the cause of electric phe- 
nomenon. 

Electricity, no matter how produced, is believed to be one 
and the same thing. 

The terms frictional electricity, pyro-electricity, magneto 
electricity, voltaic or galvanic electricity, thermo-electricity, 
contact electricity, animal or vegetable electricity, etc., etc., 
though convenient for distinguishing their origin, have no 
longer the significance formerly attributed to them as repre- 
senting different kinds of the electric force. (See Electricity, 
Hypotheses of.) 

Electricity, Conservation of A term proposed 

by Lippman, to express the fact that when a body receives an 
electric charge in the open air, the earth and heavenly 
bodies receive an equal and opposite charge, thus preserving 



WORDS, TERMS AND PHRASES. 223 

the sum of the total positive and negative electricities in the 
universe. 

Electricity, Double Fluid Hypothesis of.— A 

hypothesis which endeavors to explain the cause of electric 
phenomena by the assumption of two different electric fluids. 
The Double Fluid Electric Hypothesis assumes : 

(1) That the phenomena of electricity are due to two ten- 
uous and imponderable fluids, the positive and the nega- 
tive. 

(2) That the particles of the positive fluid repel one another, 
as do also the particles of the negative fluid ; but that the 
particles of positive fluid attract the particles of the negative, 
and vice versa. 

(3) That the two fluids are strongly attracted by matter, 
and when present in it produce electrification. 

(4) That the two fluids attract one another and unite, thus 
masking the properties of each. 

(5) That the act of friction separates these fluids, one going 
to the rubber and the other to the thing rubbed. 

Electricity, Single Fluid Hypothesi§ of. — A 

hypothesis which endeavors to explain the cause of electrical 
phenomena by the assumption of a single electric fluid. 
The single-fluid hypothesis assumes : 

(1) That the phenomena of electricity are due to the pres- 
ence of a single, tenuous, imponderable fluid. 

(2) That the particles of this fluid mutually repel one 
another, but are attracted by all matter. 

(3) That every substance possesses a definite capacity for 
holding this fluid, and, that when this capacity is just satisfied 
no effects of electrification are manifest. 

(4) That when the body has less than this quantity present, 
it becomes negatively excited, and when it has more, positively 
excited. 

(5) That the act of friction causes a redistribution of the 
fluid, part of it going to one of the bodies, giving it a surplus, 



224 A DICTIONARY OF ELECTRICAL 

and thus positively electrifying it, and leaving the other with 
a deficit, and thus negatively electrifying it. 

Neither of these hypotheses is accepted at the present 
time, electrical science having advanced sufficiently far to rec- 
ognize the fact that the exact nature of electricity is unknown. 

By some, electricity is believed to consist, like heat, of a par- 
ticular phase of energy ; by others it is regarded as an exceed- 
ingly tenuous form of matter ; by still others, the exceedingly 
strange assumption is made that it is neither a phase of energy 
nor a form of matter. 

By some, the single fluid hypothesis is provisionally ac- 
cepted with this modification, that a negatively excited body 
is thought to be the one which contains the excess of the as- 
sumed fluid, and a positively excited body the one which 
contains the deficit. 

This change in the single fluid hypothesis is believed to be 
necessitated by the fact observed in Crooke's tubes, that the 
molecules of residual gas are thrown off from the negative 
terminal, and not from the positive terminal. (See Tubes, 
Crooke's.) 

Another view, which has long been held by the author, at- 
tributes the phenomena of electricity to differences of ether 
pressures, electricity itself being the ether, and the electro- 
motive force the differences of pressure of the ether. That 
one form of electrification, possibly negative, is caused by a 
surplusage of energy charged on the excited body, thus 
producing a greater ether tension or pressure, and the oppo- 
site electrification, by a deficit of energy, thus producing a 
smaller ether tension or pressure. 

It will be seen that the assumptions as to the direction of the 
current, and the positive direction of the lines of force, are 
based on the old idea that positive electrification indicates an 
excess, and negative electrification a deficit. 

Electricity, Bound and Free, Disguised, Dissimu- 
lated, or Latent — (See Bound and Free Charge.) 



WORDS, TERMS AND PHRASES. 225 

Electrics. — Substances capable of becoming electrified by 
friction. 

Substances like the metals, which, when held in the hand 
could not be electrified by friction were called non-electrics. 

These terms were used by Gilbert in the early history of 
the science. 

This distinction is not now generally employed, since con- 
ducting substances may be electrified by friction, if insulated. 

Electrification. — The act of becoming electrified. 

Electrification generally refers to the production of an elec- 
tric charge. 

Electro-Biology. — The study of the electric conditions 
of living animals and plants, or the effects of electricity upon 
them. 

Electro-Biology includes : 

(1) Electro-Physiology. 

(2) Electro-Therapy, or Electro-Therapeutics. 
Electro-Capillary Phenomena. — Phenomena ob- 
served in capillary tubes at the contact surfaces of two liquids. 

In the case where acidulated water is in contact with 
mercury, each liquid possesses a definite surface tension, and 
each a definite shape of surface. 

The two liquids, however, do not actually touch, there being 
a small interval or space between them. This space acts as 
an accumulator. But the liquid and water, being different 
substances in contact, possess different potentials. (See Ac- 
cumulator, or Condenser. Contact, Electricity. Potential.) 

Any cause which alters the shape of these contact surfaces, 
and consequently the extent of the spaces between them, 
necessarily alters the capacity of the condenser, and conse- 
quently the difference of potential. Therefore the mere 
shaking of the tube, or heating it, will produce electric 
currents from the resulting differences of potential ; or, con- 
versely, an electric current sent across the contact-surfaces 
will produce motion as a result of a change in the value of 



326 A DICTIONARY OF ELECTRICAL 

the surface tension. An Electro- Capillary Telephone has been 
constructed on the former principle, and an Electrometer on 
the latter. (See Capillary Electrometer. Telephone, Electro-* 
Capillary.) 

Electro-Chemistry. — That branch of electric science 
which treats of chemical compositions and decompositions 
produced by the electric current. (See Electrolysis, or Elec- 
trolytic Decomposition.) 

Electrode, Indifferent In electro-thera- 
peutics the electrode that is merely employed to complete the 
circuit through the organ or part subjected to the electric 
current, and is not directly concerned in the treatment or 
diagnosis of the diseased parts. 

Either the positive or the negative electrode may be the 
indifferent electrode. (See Electrode, Therapeutic.) 

Electrode, Therapeutic — In electro-ther- 
apeutics the electrode mainly concerned in the treatment, or 
diagnosis of the diseased parts. 

Either the positive or the negative electrode may be the 
therapeutic electrode, and one or the other is employed accord- 
ing to the particular character of the effect it is desired to ob- 
tain. The other electrode is placed at any convenient and 
suitable part of the body, and is called the indifferent 
electrode. 

The therapeutic electrode is generally placed nearer the 
organ or part to be treated than the indifferent electrode. 

Electrodes. — The terminals of an electric source. 

The positive electrode is sometimes called the Anode, and 
the negative electrode the Kathode. In precise use these 
terms are generally restricted to the electrodes when used 
for electrolytic decomposition. 

The electrodes are made of different shapes and of different 
materials according to the character of the work the current 
is to perform. 



WORDS, TERMS AND PHRASES, 227 

The carbon electrodes of an arc lamp are provided for the 
formation and maintenance of the voltaic arc. In electro-ther- 
apeutics, clay electrodes, sponge electrodes, brush electrodes, 
disc electrodes, needle electrodes, dry or moist electrodes, 
urethral electrodes, aural electrodes, vaginal electrodes, rectal 
electrodes, etc., etc., are employed, and are named according 
to the nature of the work required to be accomplished, or the 
particular organ or part of the body that is to be treated. 

Electrodes, Erb's Standard Size of Standard 

sizes of electrodes generally adopted in electro-therapeutics. 

The following standard sizes have been proposed by Erb, 
viz. : 

(1) Fine electrode __ J i centimetre diameter. 

(2) Small " 2 " 

(3) Medium " 7.5 " " 

(4) Large " Gx2 

(5) Very large do .8x16 " 

Electro-Diagnosis. — Diagnosis by means of the exagger- 
ation or diminution of the reaction of the excitable tissues of 
the body when subjected to the varying influences of electric 
currents. 

The electric current has also been applied in order to dis- 
tinguish between forms of paralysis, and as a final test of 
death. 

Electro-Dynamic Induction.— (See Induction, Elec- 
tro-Dynamic.) 

Electro-Dynamics. — That branch of electric science 
which treats of the action of electric currents on one another 
and on themselves. 

The principles of electro-dynamics were discovered by Am- 
pere in 1821. 

A convenient form of apparatus, for showing experimentally 
the action of one current on another, consists of two upright 
metallic columns or pillars, which support horizontal metallic 
arms containing mercury cups, y and c, Fig. 168. The circuit 



228 



A DICTIONARY OF ELECTRICAL 



is bent in the form of a rectangle, circle, or solenoid, and ter- 
minates in points that dip in the mercury cups. The current 
is led into and out of the apparatus at the points -\- and — 
at the base of the upright supports. 

When, now, a magnet, or another circuit, is approached to 
the movable circuit thus provided, attractions or repulsions 
are produced, according to the position of the magnet, or the 
direction of the currents in the two circuits. 




If a magnet A B, Fig. 169, be placed, as shown, below the 
movable circuit C C, the circuit will tend to place itself at 
right angles to the axis of the magnet. This movement is the 
same as would occur if electric currents were circulating 
around the magnet in the direction of the assumed Amperian 
currents. (See Magnetism, Ampere's Theory of.) 



WORDS, TERMS AND PHRASES. 



229 




Ampere has given the results of his investigations in the 
following statements, which are known as Ampere's Laivs : 

(1) Parallel portions of a circuit attract one another if the 
currents in them are flowing 
in the same direction, and 
repel one another if the cur- 
rents are flowing in opposite 
directions. 

A current flowing through 
a spiral tends to shorten the 
spiral from the attraction of 
the parallel currents in con- 
tiguous turns. 

Similar poles of two sole- 
noids repel each other, as at 
A, A', Fig. 170, because, 
when opposed to each other, 
the currents that produce Fig - 169 - 

these poles are flowing in opposite directions, as may be seen 
from an inspection of the drawing. 

Dissimilar solenoid poles, on the contrary, attract each other 
as at A, B, in the figure, since the currents which produce 

them flow in the same di- 
rection. 

In Fig. 171, a form of Am- 
pere's stand is shown, in 
which one of the circuits is 
in the form of the helix M 
N ; its action on the movable 
circuit C B, is to repel it, 
A B since the currents, as shown, 

Fiff- 17 °- are flowing in opposite di- 

rections in the approached portions of the fixed and movable 
circuits. 

(2) Two portions of a circuit intersecting each other mu- 





230 



A DICTIONARY OF ELECTRICAL 



tually attract each other when the currents in both circuits 
flow either towards or from the point of intersection, but re- 
pel each other if they flow in opposite directions from the 
point. 

Thus, in Fig-. 172, the currents in both circuits flow towards 
and from the point of intersection Y, and attract one another 
and cause a motion until the two circuits arc parallel. 




Fig. 171. 

If the currents flow in opposite directions they repel one 
another, and, if free to move, will come to rest when parallel 
to each other ; therefore, two portions of a circuit crossing- 
each other tend to move until they are parallel, and their cur- 
rents are flowing in the same direction. 

(3) Successive portions of the circuit of the same rectilineal 
current, that is, a current flowing in the same straight line, re- 
pel one another. 

Continuous Rotations by Currents. — A circuit O A, Fig. 173, 
movable on O, as a centre, will be continuously rotated in the 
direction of the curved arrow by the rectilinear current, P Q ; 



WORDS, TERMS AND PHRASES. 



231 




for, the directions of the currents being- as shown by the ar- 
rows, there will be attraction in the positions (1) and (2), and 
repulsion in position (4). 

The cause of the mutual attractions and repulsions of elec- 
tric circuits will readily appear 
from a consideration of the mutual 
action of their magnetic fields. 

Thus an inspection of Fig-. 174, 
shows : 

(1) That parallel currents flow- 
ing in the same direction attract, 
because their lines of force have 
opposite directions in adjoining 
parts of the circuit. 

(2) That parallel currents flow- P. 
ing in opposite directions repel, 
because their lines of force have 
the same direction in adjoining 
parts of the circuit. Fi Q- I7f - 

These laws may therefore be generalized thus, viz.: Lines 
of force extending in opposite directions attract one another: 
lines of force extending in the same 
direction repel one another. 

Ampere proved that a circuit, doubled 
on itself so that the current flows in 
opposite directions in the two parts, 
exerts no force on external objects. 
This expedient is adopted in resistance 
p Q coils to prevent any disturbance of the 

Fig. 173. galvanometer needles. He also showed 

that a sinuous circuit, or one bent into zigzags, produces the 
same effects of attraction or repulsion as it would if it were 
straight. (See Coils, Resistance.) 

The term sinuous current is often applied to the current in 
such a conductor. (See Currents, Sinuous.) 




232 



A DICTIONARY OF ELECTRICAL 



Electro-Dynamometer.— (See Dynamometer, Electric.) 
Electro-Etching.— (See Engraving, Electric). 
Electrokinetics. — A term sometimes applied to the phe- 
nomena of electric currents, or electricity in motion, as dis- 
tinguished from Electrostatics, the phenomena of electric 
charges, or electricity at rest. 

Electrolier. — A chandelier for electric lights, as dis- 
tinguished from a chandelier for holding gas lights. 

Electrolysis, Faraday's Laws of The prin- 
cipal facts of electrolysis are given in the following laws : 

(1) The amount of chemical action in any given time is equal 
in all parts of the circuit. 




Fig. m. 

(2) The amount of any ion liberated in a given time, is pro- 
portional to the strength of the current passing. Twice as 
great a current will liberate twice as much of an ion. 

(3) When the same current passes successively through 
several cells containing different electrolytes, the weights of the 
ions liberated at the different electrodes are equal to the 
strength of the current multiplied by the electro-chemical 
equivalent of the ion. 

The electro-chemical equivalent is equal to the atomic weight 
divided by the valency. (See Equivalent, Electro- Chemical.) 



WORDS, TERMS AND PHRASES. 233 

Electrolysis, or Electrolytic Decomposition.— 

Chemical decompositions effected by means of the electric 
current. 

When an electric current is sent through an electrolyte, i. e., 
a liquid which permits the current to pass only by means of the 
decomposition of the liquid, the decomposition that ensues 
is called electrolytic decomposition. 

The electrolyte is decomposed or broken up into atoms or 
groups of atoms or radicals, called ions. 

The ions are of two distinct kinds, viz.: the electro-positive 
ions, or kathions or kations, and the electro-negative ions 
or anions. 

Since the anode of the source is connected with the electro- 
positive terminal, it is clear that the anions, or the electro- 
negative ions, must appear at the anode, and the kathions, or 
the electro-positive ions, must appear at the kathode. 

Hydrogen, and the metals generally, are kathions ; oxygen, 
chlorine, iodine, etc., are anions. 

The vessel containing the electrolyte, in which these de- 
compositions take place, is called an electrolytic cell. 

An electrolytic cell is called a voltameter, when it is 
arranged for measuring the current passing by means of 
the amount of decomposition it effects. (See Voltameters.) 

Electrolytic Convection.— (See Convection, Electro- 
lytic.) 

Electro-Hagiiet. — A magnet produced by the passage of 
an electric current through a coil of insulated wire surround- 
ing a core of magnetizable material. 

The magnetizing coil is called a helix or solenoid. (See Mag- 
netism, Ampere s Theory of. Solenoid, Electro-Magnetic.) 

Strictly speaking, the term electro-magnet is limited to the 
case of a magnet provided with a soft iron core, which is thus 
enabled to rapidly acquire its magnetism on the passage of the 
magnetizing current, and as readily to lose its magnetism on 
the cessation of such current. 



234 



A DICTIONARY OF ELECTRICAL 



Aii electric current passed around a bar of magnetizable 
material, in the manner and direction shown in Fig. 175, will 
produce a polarity at its ends or extremities. 

The direction of this polarity may be predicted by the fol- 
lowing- modifications of a rule proposed by Ampere : 




Fig. 175. 

Imagine yourself swimming in the wire in the direction of 
the current; if, then your face is directed towards the bar 
that is being magnetized, its north seeking pole will be on 
your left. 

If, for example, the conductor A B be traversed by a cur- 
rent in the direction from B to A, as shown in Fig. 177, 
the north pole N, of the needle N S, placed under the con- 
ductor, is deflected, as shown, to the left of the observer, who 
is supposed to be swimming in the current, facing the needle. 
If the current flow in the opposite direction, as from A to B, as 
shown in the Fig. 178, the N pole of the needle is deflected as 
shown, but still to the left of the observer supposed to be swim- 
ming as before. 

The directions of currents required to produce N and S poles 
respectively, are shown in Fig. 176. 

The cause of this direction of polarity will be readily un- 
derstood from a study of the direction of lines of magnetic 
force in the field produced by an electric current. 



WORDS, TERMS AND PHRASES. 



235 



In any electric circuit, the lines of magnetic force, produced 
by the passage of the current, 
form circles around the circuit 
in planes at right angles to 
the direction of the current, 
as shown in - Fig. 179. The 
direction of these lines of 
force is the same as that of 
the hands of a watch, if the Fig - 176 ' 

current be supposed to flow away from the observer. (See 
Field, Magnetic, of an Electric Current.) 






B 

Fig. 178. Fig. 177. 

Remembering now that the lines of force are supposed to 
come out of the north pole and to pass into the south pole, 
it is evident that if the current flows in the direction shown in 
Fig. 180, the lines of force will come out of the north pole 
and pass into the south pole. 



236 



A DICTIONARY OF ELECTRICAL 



Since in a right handed helix the wire passes around the 
axis in the opposite direction to that in which it passes in a left 
handed helix, it is evident that the helices shown in Fig. 181 
v a at 1 and 2, will 

produce opposite 
polarities at the 
points of entrance 
and exit by a cur- 
rent flowing in the 
direction of the ar- 
Fig. 179. rows. 

If the current be sent through the right handed helix, shown 
at 1, from b to a, that is, from the left to the right in the figure, 
a south pole will be produced at b, and a north pole at a. 
If, however, it be sent from a to b, the polarity will be re- 
versed. 

< 





Fig. 180. 

If the current be sent through the left handed helix, shown 
at 2, from a, to b, that is, from the left to the right in the figure, 
a north pole will be produced at a, and a south pole at b. If, 



WORDS. TERMS AND PHRASES. 



237 



however, it be sent in the opposite direction the polarity will 
be reversed. 

Therefore, in an electro magnet, on the core of which 
several layers or thicknesses of wire are wound, in which 
the current flows through one layer, in, say a direction from 
right to left, it must return through the next layer in the 
opposite direction, or from left to right. The polarities of the 
same extremities of the helices are, however, the same in all 
cases, since the layers are successively right and left handed. 
The winding at 3 produces a number of consequent poles. 

Electro-Magnets, Laws of. 




o a 

Fig. 181. 

(1) The magnetic intensity (strength) of an electro magnet 
is nearly proportional to the strength of the magnetizing 
current, provided the core is not saturated. 

(2) The magnetic strength is proportional to number of turns 
of wire in the magnetizing coil. 

(3) The magnetic strength is independent of the thickness or 
material of the conducting wires. 

These laws may be embraced in the more general statement 
that the strength of an electro magnet, the size of the magnet 
being the same, is proportional to the number of its Ampere 
Turns. (See Ampere-Turns.) 



238 A DICTIONARY OF ELECTRICAL 

A short interval of time is required for a current to 
thoroughly magnetize a powerful electro-magnet. 

A few moments are also required for a powerful magnet to 
thoroughly lose its magnetism. At the same time, electro 
magnets are capable of acquiring or losing their magnetism 
several thousand times a second. It is, in fact, on this ability 
possessed to so remarkable a degree by soft iron, that the value 
of an electro magnet for many purposes depends. (See Lag, 
Magnetic.) 

Electro-Magnetic Annunciator.— (See Annunciator, 
Electro-Magnetic. ) 

Electro-Magnetic Dental Mallet.— (See Dental Mal- 
let, Electro-Magnetic.) 
Electro-Magnetic Drill.— (See Drill, Electro-Magnetic.) 

Electro-Magnetic Engine.— (See Engine, Electro-Mag- 
netic.) 

Electro-Magnetic Induction.— A variety of electro- 
dynamic induction in which electric currents are produced by 
the motion of electro magnets, or electro-magnetic solenoids. 
(See Induction, Electro-Dynamic.) 

Electro-Magnetic Solenoid.— (See Solenoid, Electro- 
Magnetic.) 

Electro-Magnetic Stress The force or pres- 
sure in a magnetic field which produces a strain or deformation 
in a piece of glass or other similar substance placed therein. 
(See Optical Strain, Electro-Magnetic.) 

Electro-Magnetics. — That branch of electric science 
which treats of the relations between electric currents and 
magnets. 

Electro-Metallurgy.— Metallurgical processes effected 
by the agency of electricity. 

Electro-Metallurgy embraces : 

(1) The Reduction of Metals from their ores, either directly 
from their fusion by the heat ol the voltaic arc, or the heat of 



WORDS, TERMS AND PHRASES 



239 



incandescence, or by the electrolysis of solutions of their ores. 
(See Electrolysis. Furnace, Electric.) 

(2) Electroplating. 

(3) Electrotyping. 

The application of electricity to the reduction of metals is 
carried on in the electric furnace for the reduction of the 
aluminium ores. 

Electrometer. — An apparatus for measuring- differences 
of potential. 

Electrometers, operate in general, by means of the attraction 
or repulsion of charged conductors on a suitably suspended 
needle or disc. As no current is required to flow through the 
apparatus it is adaptable to many cases where a voltmeter 
could not be so readily used. 

Electrometer, Absolute A form of attracted 

disc electrometer. (See Electrometer, Attracted Disc.) 

Electrometer, Attracted Disc A form of 

electrometer de- 
vised by Sir Wm. Q 
Thomson, in 
which the force 
is measured by 
the attraction be- 
tween two discs. 

Thomson's At- 
tracted Disc Elec- 
t r o m e t e r is 
shown in Fig. 182. 
It consists of a 
plate C, suspend- Fig. 182. 

ed from the longer end of a lever I, within the fixed guard 
plate, or guard ring, B, immediately above a second plate 
A, supported on an insulated stand, and capable of a meas- 
urable approach towards C, or a movement away from it. 
The plate C, is placed in contact with B, by means of a thin 




240 



A DICTIONARY OF ELECTRICAL 




wire. By means of this connection the distribution of the 
charge over the plate C, is uniform. The electrostatic at- 
t traction is measured by the attrac- 

tion of the fixed disc A, or the 
movable disc C. The fulcrum of 
the lever 1, is formed of an alu- 
minium wire, the torsion of which 
is used to measure the force of the 
attraction, or, it may be meas- 
ured directly by the counterpoise 
^re^X^N}^^ weight Q. 

Fig. 183. This instrument is called an ab- 

solute electrometer, because, knowing the dimensions of the 
apparatus, the value of the electro-motive force can be directly 
determined from the amount 
of the motion observed. 

Electrometer, Capil- 
lary , —(See Capillary 

Electrometer.) 

Electrometer, Quad- 
rant ■ —An electro- 
meter in which the electro- 
static charge is measured by 
the attractive force of plates 
or quadrants, a, b, c, d, Fig. 
183, on a light needle u, of 
aluminium suspended within 
them. 

The sectors or quadra*nts 
are of brass, and are so 
shaped as to form a hollow 
cylindrical box when placed 
tog-ether. The four sectors 
or 




Fig. 18U. 



quadrants, are insulated from one another, but the op- 
posite ones are connected by a conducting wire, as shown 



WORDS, TERMS AND PHRASES. 



241 



in Fig. 183. A light needle of aluminium that is main- 
tained at some constant potential, by connection with the 
inner coating of a Leyden jar, is generally suspended by two 
parallel silk threads, so that it freely swings inside the hollow 
box, and, when at rest, is in the position, as shown by the 
dotted lines, with its axis of symmetry exactly under one of 

the slots or spaces be- 
tween the opposite sec- 
tors. (See Bi-Filar Sus- 
pension.) 

The quadrant electro- 
meter is shown in Fig. 

184, with one of the 
quadrants removed so as 
to show the suspended 
aluminium needle. 

A similar form of in- 
strument is shown in Fig. 

185, with all the quad- 
rants in place, and cov- 
ered by a glass shade. 

To use the.instrument, 

the sectors are connected 

with the source whose 

difference of potential is 

to be measured, and the 

deflection of the needle 

~-s/*- - j^ observed, through a tele- 

■^ scope, by means of a spot 

Fi 9- 185 - of light reflected from a 

mirror attached to the upper part of the needle. 

Sometimes the segments are made in the shape of a cylin- 
der, and the needle in the shape of a suspended rectangle. 
Electro-Motive Force, or E, M, F.— The force that 
causes electricity to move, 




242 



A DICTIONARY OF ELECTRICAL 



The term electro-motive force is generally written thus : 
E.M.F. 

The electro-motive force is due to a difference of electrical 
level or potential. In the current that results, the flow is as- 
sumed to be directed from the higher to the lower level, just 
as in the case of liquids. (See Potential.) 

The term electro-motive force should not be used as entirely 
synonymous with difference of potential. The electro-motive 
force of any source is only correctly applied to the total gen- 
erated difference of potential. Anything less than this at 
various parts of the circuit is more correctly spoken of as a 
Terence of potential. 

The unit of electro-motive force is the volt. (See Volt.) 




-(See Aver- 



Fig. 186. 

Electro-Motive Force, Average 

age Electro-Motive Force.) 

Electro-Hotive Force, Counter or Back 

—(See Counter Electro-Motive Force.) 

Electro-Motograph. — An apparatus invented by Edison 
whereby the friction of a platinum point against a rotating 
cylinder of moist chalk is reduced by the passage of an electric 
current, 



WORDS, TERMS AND PHRASES. 243 

This result is due to an electrolytic action at the points of 
contact, varying- the friction. 

Edison has constructed a telephone on this principle. The 
electro-motograph, though less certain in its action than an 
electro-magnet, may replace it in certain electric apparatus. 

The detailed construction of the electro-motograph may be 
understood from an inspection of Fig. 186. 

The lever A, pivoted with a universal joint at C, has a 
metallic point at its free extremity F, resting on a strip of 
moistened paper N, and held against it with some pressure 
by the action of the spring S. The paper N rests on the 
metallic drum G, over which it is moved in the direction of 
the arrow on the rotation of the drum by clockwork. A 
spring R acts to move the lever A in a direction opposite to 
that in which it tends to move by the rotation of the 
drum G. 

The main battery L is connected at its negative pole to 
the point F and at its positive pole, through the key K, to 
the metallic drum G. The local battery L B, is connected 
through the sounder X to the contacts D and X. 

When the key K is open, the friction of F on the paper, 
N, is sufficient to move the lever A to the right so as to close 
the circuit of the local battery ; but when the key K is de- 
pressed, the current of L, passing through the paper, decom- 
poses the chemicals with which it is moistened, lessens the 
friction of the point F, and permits the spring B, to draw 
the iever A, to the left, thus opening the circuit of the local 
battery L B. 

The movements of the key are therefore reproduced by the 
armature of the electro-magnet X. 

Electro-Muscular Excitation.— In electro therapeu- 
tics the galvanic or faradic excitation of the muscle, or its ex- 
citation by the continuous currents of a voltaic battery, or the 
alternating currents of an induction coil. 

Electro-Optics.— (See Optics, Electro.) 



244 



A DICTIONARY OF ELECTRICAL 




Electropliorus. — An apparatus for the production of elec- 
tricity by electrostatic induction. (See Induction, Electrostatic.) 
A disc of vulcanite, or hard rubber B, contained in a 
metallic form, is rubbed briskly by a piece of cat's skin and 
the insulated metallic disc A, is placed on 
the centre of the vulcanite disc, as shown 
in Fig. 187. 

The negative charge produced in B by 
the friction, produces by induction a pos- 
itive charge on the part of A nearest it, 
and a negative charge on the part furthest 
from it. 

In this condition, if the disc be raised 
from the plate by means of its insulating 
Fig. 187. handle, as shown in Fig. 188, no electrical 

effects will be noticed, since the two opposite and equal charges 
unite and neutralize each other. If, however, the disc Abe first 
touched by the finger, and then raised 
from the disc B, it will be found to be 
positively charged. 

EIectro-Phy§ioIogy.— The study 
of the electric phenomena of living an- 
imals and plants. 

Living animals and plants present 
electric phenomena, due to the electricity 
naturally produced by them. It is the 
study of electro-physiology to ascertain 
the causes and effects of these phe- 
nomena. 

Electro-Plating. — The process of covering any electri- 
cally conducting surface with a metal by the aid of the elec- 
tric current. 

By the aid of electro-plating, the baser metals are covered 
with silver, nickel, or copper, or with any other metal, such as 
gold, or platinum? 




Fig, 



WORDS, TERMS AND PHRASES. 245 

The process of electro-plating is carried on as follows : 

The object to be plated is connected with the negative termi- 
nal of a battery and placed in a solution of the metal with 
which it is to be plated, opposite a plate of that metal con- 
nected to the negative terminal of the battery. If, for ex- 
ample, the object is to be plated with copper it is placed in a 
solution of copper sulphate or blue vitriol, opposite a plate of 
copper. By this arrangement the object to be plated forms 
the kathode of the plating bath, and the plate of copper 
forms the anode. 

On the passage of the current the copper sulphate (Cu S0 4 ) is 
decomposed, metallic copper being deposited in an adherent 
layer on the articles attached to the kathode, and the acid rad- 
ical (S0 4 ) appearing at the anode, where it combines with one 
of the atoms of the copper plate. Since for every molecule of 
copper sulphate decomposed in the electrolyte, a new mole- 
cule of copper sulphate is thus formed, by the gradual solu- 
tion of the copper anode, the strength of the solution in the 
bath is maintained as long as any of the copper plate remains 
at the anode, and the ordinary activity of the cell is not 
otherwise interfered with. 

When any other metals such as gold, silver, or nickel, for ex- 
ample, are to be deposited, suitable solutions of their salts are 
placed in the bath, and plates of the same metal hung at the 
anode. 

The character and coherence of the metallic coatings thus 
obtained depend on the nature and strength of the plating- 
bath, and on the density of the current employed. The size 
and position of the anode, as compared with that of the objects 
to be plated, must therefore be carefully attended to, as well 
as the strength of the metallic solution and the current 
strength passing. (See Density of Current.) 

Fig. 189. shows a bath arranged for silver-plating. 

The anode consists of a plate of silver. The spoons, forks, 
etc., to be plated are immersed in a suitable silver solution 
and connected with the kathode. 



246 



A DICTIONARY OF ELECTRICAL 



The electrotyping process is employed for the production of 
electrotype plates. It was called by Jacobi, the galvano- 
plastic process. The term electrotyping is however more gen- 
erally adopted. 

Electro-Pneumatic Signals.— (See " Signals;' Electro- 
Pneumatic.) 

Electropoion Liquid.— A battery liquid consisting- of 
one pound of bichromate of potash dissolved in ten pounds of 
water, to which two and one-half pounds of commercial sul- 
phuric acid have been gradually added. 

This liquid is employed with the carbon-zinc cell or the bi- 
chromate of potash cell. 




Fig. 189. 

Electro - Puncture, or Galvano - Puncture.— The 

application of electrolysis to the treatment of aneurisms, or 
diseased growths. 

The blood is decomposed by the introduction of a fine plati- 
num needle connected with the anode of a battery and insu- 
lated, except near its point, by a covering of vulcanite. 

The kathode is a sponge covered metallic plate. 



WORDS, TERMS AND PHRASES. 



247 



Electro-Receptive Devices.— (See Devices, Electro- 
Receptive.) 

Electroscope. — An apparatus for showing the presence 
of an electric charge, or for determining- its sign, whether 
positive or negative, but not for measuring the value of the 
charge. 

In the gold leaf electroscope, two gold leaves, n n> Fig. 190, 
suspended near one another, show by their repulsion the 
presence of a charge. Two pith balls may be used for the 
same purpose. 




Fig. 190. Fig. 191. 

To use an electroscope for determining the signoi a charge, 
the gold leaves or pith balls are first slightly repelled by a 
charge of known name, as, for example, positive, applied to 
the knob C. They are then charged by the electrified body 
whose charge is to be determined. If they are farther re- 
pelled, its charge is positive. If they are first attracted and 
afterwards repelled, its charge is negative. 

Similarly, if the pith balls, B B, shown in Fig. 191, re- 
pelled by a known charge, be approached by a similar charge 
in S, they will at once be still further repelled, as shown by 
the dotted liues. 

Two posts B, Fig. 190, connected with the earth, increase the 
amount of divergence by induction. 



248 



A DICTIONARY OF ELECTRICAL 



Electroscope, Condensing, 



Volta's.— An 



electroscope employed for the detection of feeble charges, the 
leaves of which are charged by means of a condenser. 

The condensing electroscope, Fig. 192, is formed of two me- 
tallic plates, placed at the top of the instrument, and separated 
by a suitable dielectric. The upper plate P, is removable by 
means of the insulated handle G. 
To employ the electroscope, as for 
example, to detect the free charge in 
an unequally heated crystal of tour- 
maline the crystal is touched to the 
lower plate, while the upper plate is 
connected to the ground by the finger. 
On the subsequent removal of the 
upper plate, an enormous decrease 
ensues in the capacity of the conden- 
ser, and the charge now raises the 
potential of the lower plate, and 
causes a marked divergence of the 
leaves, L L. (See Pyro-Electricity.) 
Quadrant Henley's.— An 




Fig. 192. 

Electroscope, 



electroscope sometimes employed to indicate large charges of 
electricity. 

A pith ball placed on a light arm A, of straw or other 
similar material, Fig. 193, is pivoted at the centre of a gradu- 
ated circle B. The arm C is attached by means of the screw 
to the prime conductor of an electric machine. The similar 
charge imparted to A by contact with C, causes a repulsion 
which may be measured on the graduated arc. 

This instrument approaches the electrometer in its opera- 
tion, since by its means simple measurements may be made of 
the value of the repulsion. It should not, however, be con- 
founded with the quadrant electrometer. (See Electrometer, 
Quadrant.) 

Electrostatic Field. — (See Field, Electrostatic.) 



WORDS. TERMS AND PHRASES. 



249 



Electrostatic Induction.— (See Induction, Electro- 
static.) 

Electrostatic Induction Machines. — (See Machines, 
Electrostatic Induction.) 

Electrostatic Lines of Force. — (See 
lines of Force, Electrostatic.) 

Electrostatic Stress.— The force, or 
pressure in an electric field which produces 
a strain or deformation in a piece of glass or fcps/g 
similar body placed therein. (See Optical 
Strain, Electrostatic.) 

Electrostatics. — That branch of electric 
science which treats of the phenomena and 
measurement of electric charges. 

The principles of electrostatics are em- 
braced in the following laws, viz. : 

(1) Charges of like name, i.. e., either pos- 
itive or negative, repel each other. Charges 
of unlike name attract each other. 

(2) The forces of attraction, or repulsion 
between two charged bodies are directly pro- 
portional to the product of the quantities of 
electricity possessed by the bodies and in- 
versely proportional to the square of the dis- 
tance between them. 

These laws can be demontsrated by the 
use of Coulomb's torsion balance. (See Bal- 
ance, Torsion.) p . g m 

Electro-Therapeutic Bath.— (See Bath, Electro-Ther- 
apeutic.) 

Electro-Therapeutics, or Electro-Therapy.— The 

application of electricity to the curing of disease. (See Elec- 
ro-Biology). 



256 A DICTIONARY OF ELECTRICAL 

Electro-Therapy, or Electro-Therapeutics.— The 

application of electricity to the treatment of disease. 

Electrotonus.— A condition of altered functional activity 
which occurs in a nerve when subjected to the action of an 
electric current. 

This alteration may consist in either an increased or a 
decreased functional activity. The decreased functional 
activity occurs in the neighborhood of the anode or the posi- 
tive terminal, and is called the anelect rotonic state. The in- 
creased functional activity occurs in the neighborhood of the 
kathode, or the negative terminal, and is called the kathelec- 
trotonic state. (See Anelectrotonous. Kathelectrotonous.) 

Electro typing, or the Electrotype Process. — Ob- 
taining casts or copies of objects by depositing metals in 
moulds by the agency of electric currents. 

The moulds are made of wax, or other substance, rendered 
conducting by mixing with powdered plumbago. 

The mould is connected with the negative battery terminal, 
and placed in a metallic solution, generally copper sulphate, 
opposite a plate of the same metal, connected with the positive 
battery terminal. As the current passes, the metal is de- 
posited on the mould at the kathode, and dissolved from the 
metallic plate at the anode, thus maintaining constant the 
strength of the bath. 

Element, Negative (See Couple, Voltaic.) 

Element of Current. — (See. Current, Element of .) 
Element, or Elementary Matter. — Matter which can- 
not be decomposed into simple matter. 
Matter that is formed or composed of but one kind of atoms. 
Oxygen and hydrogen are elements, or varieties of ele- 
mentary matter. They cannot be decomposed into anything 
but oxygen or hydrogen. Water, on the contrary, is com- 
pound matter, since it can be decomposed into its constituent 
parts, oxygen and hydrogen. 



WORDS, TERMS AND PHRASES. 



251 



There are about seventy well known elements, some of 
which are very rare, occurring in extremely small quantities. 

The evidence of the true elementary condition of many of 
the elements is based, to a great extent, on the fact that so 
far they have resisted all efforts made to decompose them 
into simpler substances. We should bear in mind, however, 
that until Davy's use of the voltaic battery, potash, soda and 
many other similar compounds were regarded as true ele- 
ments. It is therefore not improbable that many of the now 
so-called elements, may hereafter be decomposed into simpler 
constituents. 

Element, Positive —(See Couple, Voltaic.) 

The following tables give the names, chemical symbols, 
equivalents and specific gravities of the principal elements. 
Simple Substances, with their Symbols, Equivalents and 
Specific Gravities. 



Name. 


Symbol. 


Equiv. 


Sp. Grav. 


Aluminium _. 


Al 
Sb 
As 
Bi 
Bi- 
Cd 
Ca 
C 
CI 
Co 
Cu 
F 

Au 
H 
I 

Ir 
Fe 
Pb 
Mg 
Mn 


13.7 
64.6 
37.7 
71.5 
78.4 
55.8 
20.5 
6.1 
35.5 
29.5 
31.7 
18.7 

196.6 
1.0 

126.5 
98.5 
28.0 

103.7 
12.7 
26.0 


2.56 


Antimony 


6.70 


Arsenic _ 


5.70 


Bismuth 


9.82 


Bromine 


3.00 


Cadmium 


8.65 


Calcium . . 


1.58 


Carbon 


3.50 


Chlorine 


2.44 


Cobalt 


8.53 


Copper 


8.80 


Fluorine 


1.32 


Gold (aurum) . 


19.30 


Hvdrogen 


0.069 


Iodine 


4.94 


Iridium __ 


18.68 


Iron_. __ 


7.75 


Lead _. 


11.35 


Magnesium 


1.75 


Manganese 


8.00 



252 



A DICTIONARY OF ELECTRICAL 



Name 

Mercury 

Molybdenum 

Nickel _ 

Nitrogen 

Osmium _ _ 

Oxygen 

Palladium ___ 

Phosphorus 

Platinum _ . . 

Potassium 

Rhodium 

Selenium 

Silver 

Sodium 

Strontium 

Sulphur 

Tellurium 

Tin 

Titanium 

Tungsten 

Uranium 

Zinc _ 



Symbol. 



Equiv. Sp. Grav. 



Hg 

Mo 

Ni 

N 

Os 

O 

Pd 

P 

Pt 

K 

R 

Se 

Ag 

Na 

Sr 

S 

Te 

Sn 

Ti 

W 

U 

Zn 



200.0 
47.9 
29.5 
14.2 
99.7 
8.0 
53.3 
15.9 
98.8 
39.2 
52.2 
40.0 

108.3 
23.5 
43.8 
16.1 
64.2 
58.9 
24.5 
92.0 
60.0 
32.3 



13.50 
8.60 
8.80 
0.972 

10.00 
1.102 

11.35 
1.77 

21.50 
0.865 

11.00 
4.5 

10.5 
0.972 
2.54 
1.99 
6.30 
7.29 
5.28 

17.00 

10.15 
7.00 



Element, Thermo-Electric 



Clark & Sabine. 
-One of the metals 



or substances which forms a thermo-electric couple. (See Cou- 
ple, Thermo-Electric.) 

Element, Voltaic One of the metals or sub- 
stances which forms a voltaic couple. (See Couple, Voltaic.) 

Elements, Electrical Classification of A 

classification of the elements into two groups or classes ac- 
cording to whether they appear at the anode or kathode when 
electrolyzed. 

The chemical elements may be arranged into electro-positive 
and electro-negative according to whether, during electrolysis, 
they appear at the negative or positive terminal of the source. 

The electro-positive elements or radicals are called Jcathions, 



WORDS. TERMS AND PHRASES. 253 

and appear at the kathode or electro-negative terminal. The 
electro-negative elements are called anions, and appear at the 
anode or the electro-positive terminal. (See Ions.) 

The metals generally are electro-positive ; oxygen, chlorine, 
iodine, fluorine, etc., are electro-negative. 

Elongation, Magnetic — An increase in the 

length of a bar of iron on its magnetization. 

This increase in length is thought to greatly strengthen 
Hughes' theory of magnetism. (See Magnetism, Hughes' 1 
Theory of.) 

Embosser, Telegraphic An apparatus for re- 
cording a telegraphic message in raised or embossed characters. 

E. M. F. — A contraction generally used for the word 
electro-motive force. 

Energy. — The power of doing work. 

The amount of work done is measured by the product of the 
force, and the space through which it moves. Thus one 
pound raised vertically through ten feet, ten pounds raised 
through one foot, or five pounds raised through two feet, all 
represent the same amount of work, viz., ten foot pounds. 

If a weight of ten pounds be raised through a vertical 
height of one foot, by means of a string passing over a pulley, 
there will have been expended an amount of energy repre- 
sented by the work of ten foot pounds. If the weight be pre- 
vented in any way from falling, as by tying the string, it will 
have stored in it an amount of energy equal to ten foot 
pounds, and if permitted to fall, is capable of doing an 
amount of work which, leaving out air resistance and friction, 
is exactly equal to that expended in raising it to the position 
from which it falls, viz., ten foot pounds of work. 

Energy, Actual, Kinetic Energy, Energy of 

Motion. — Energy employed in doing work, or the power of 
doing work possessed by bodies that are in motion, 



254 A DICTIONARY OF ELECTRICAL 

Energy, Atomic or Chemical Potential — The 

potential energy possessed by the elementary chemical atoms. 
(See Energy, Potential.) 

Energy, Conservation of —(See Conservation 

of Energy.) 

Energy, Degradation of (See Degradation of 

Energy.) 

Energy, Electric The power which electricity 

possesses of doing work. 

In the case of a liquid surface at different levels, the liquid 
at the higher level possesses a certain amount of potential 
energy measured by the quantity of the liquid at the higher 
level, and the excess of its height over that of the lower level ; 
or, on the difference of level between them. This difference of 
level will produce a current from the higher to the lower level, 
and during the passage of the current, potential energy will 
be lost, and a certain amount of work will be done. 

In the case of electricity, the difference of electric level or 
potential, between any two points of a conductor, causes an 
electric current to flow between these points from the higher 
to the lower electric level, during which electric potential 
energy is lost, and work is accomplished by the current. (See 
Potential.) 

The amount of the electric work is measured by the quantity 
of electricity that flows, multiplied by the difference of poten- 
tial under which it flows. (See Joule, or Volt- Coulomb.) 

Electric energy, however, is generally measured in electric 
power, or rate of doing electric work. 

Since an ampere is one coulomb per second, if we measure 
the difference of potential in volts, the product of the amperes 
by the volts will give the electrical power in volt-amperes, or 
watts, or units of electric power. CE = The Watts. (See 
Ampere. Volt. Watt.) 

Que horse-power equals 550 foot pounds per second. One 



WORDS, TERMS AND PHRASES. 255 

watt or volt-ampere = ^ of a horse-power, or one horse- 
power equals 746 volt-amperes or watts, therefore : 

The current in amperes, multiplied by the difference of po- 
tential in volts, divided by 746, equals the rate of doing work 
in horse-power. 

Thus, if .7 ampere is required to operate a 16 candle, 110 
volt, incandescent lamp, it requires 4.8 watts per candle. 
One Watt = 44.2394 foot-pounds per minute. 
One Watt = .737324 foot-pounds per second. 
The Heat Activity, or the heat per second produced by an 
electric current, is also proportional to the product C E, or the 
watts, for the heat is proportional to the square of the current 
in amperes multiplied by the resistance in ohms, or C 2 R = 
the Heat. (See Calorimeter, Electric.) 
By Ohm's Law (See Ohm's Law), 
E 
C - — (1), or C R = E , (2), 
R 
but the electric power or the watts = CE (3). 

If, now, we substitute the value of E, taken from equation 
(2) in equation (3) we have 

CE = C X CR = C 2 R; 
therefore C 2 R = watts. 

To determine the heating power of a current in small cal- 
ories, calling- H, the amount of heat required to raise 1 
gramme of water through 1° Cent., and C, the current in 
amperes. 

H = C 2 R X .24. 
Or, for any number of seconds, t, 

H = C 2 ~Rt X -24, 
Therefore, one watt = .24 calories per second. (See Calorie.) 
But from Ohm's law, 

E 
C = - (1), 
R 

and the formula for electric power or the watts = CE , (2) 



256 A DICTIONARY OF ELECTRICAL 

By substituting in equation (2) and the value of C in equation 

(1), 

E E 3 
CE = EX — = — = watts. 
R R 
That is to say, the electric power, in any part of a circuit 
varies directly as the square of the electro-motive force. 

We therefore have three expressions for the value of the 
watt or the unit of electric power, viz. : 
CE= watts. (1) 

C 2 R = watts. (2) 
E 2 

— == watts. (3) 

R 

(1) C E = Watts ; or the electric power is proportional to 
the product of the quantity of electricity per second, 
that passes, in amperes, and the difference of electric poten- 
tial or level, through which it passes, in volts. 

(2) C 2 R = Watts ; or the electric power varies directly as 
the resistance R, when the current is constant, or as the 
square of the current, if the resistance is constant. That is 
to say, if with a given resistance, the power of a given current 
has a certain value, and the current flowing through this same 
resistance be doubled, the power is four times as great, or is 
as the square of the current. 

E 2 

(3) — = Watts, or the electric power is inversely as the re- 

R 
sistance R, ivhen the electro-motive force is constant. 

A circuit of one ohm resistance will have a power of one watt, 
when under an electric motive force of one volt, since it would 
then have a current of one ampere flowing through it, and 
C E = 1. If, however, the resistance be halved or becomes .5 
ohm, then two amperes pass, or the power equals 2 watts. 

The power varies as the square of the electro-motive force 
in any part of a circuit, when the resistance is constant in 



WORDS, TERMS AND PHRASES". 257 

that part. Thus 2 amperes, and 2 volts, in a circuit of one 
ohm resistance, give a power, CE = 2 X 2 =4 walls. If now, 
R, remaining the same, the electro-motive force be raised to 4 
volts, then since E is doubled, (', or the amperes are doubled, 

E a 16 

and CxE = 4x4 = l(i watts, or — = — = 16. 

R 1 

Energy, Electric Transmission of ■ — The 

transmission of mechanical energy between two distant 
points connected by an electric conductor, by converting- the 
mechanical energy into electrical energy at one point, send- 
ing the current so produced through the conductor, and recon- 
verting the electrical into mechanical energy at the other 
point. 

A system for the electric transmission of energy embraces : 

(1) A Conducting Circuit between two stations. 

(2) An Electric Source, or battery of electric sources, or 
machines, at one of the stations, generally in the form of a 
dynamo-electric machine, for converting mechanical energy 
into electric energy. 

(3) Electro-Receptive Derives, generally electric motors, at 
the other station for reconverting the electric into mechanical 
energy. (See Motors, Electro- Magnetic.) 

Energy, Potential, Energy of Position, 

Static Energy, or Energy of Stress. — Stored energy ; 
potency or capability of doing work. 

The capacity for doing work possessed bj- a body at rest, 
arising from its position as regards the earth, or from the pos- 
ition of its atoms as regards other atoms. 

A pound of coal if raised vertically one foot, possesses, as a 
mere weight, an amount of energy capable of doing an amount 
of work equal to one foot pound. The atoms of carbon, how- 
ever, of which it is composed, have been raised or separated 
from those of oxygen, or some other elementary substance, 
and when the coal is burned, or the carbon atoms fall towards 



258 A DICTIONARY OF ELECTRICAL 

the oxygen atoms (i.e., unite with them), the coal gives up 
the potential energy of its atoms in the form of heat. 

All elementary substances possess in the same way atomic, 
or chemical potential energy, or the energy with which they 
tend to fall together. This energy varies in amount in differ- 
ent elements and becomes kinetic, as heat, on combination 
with other elements. 

Engine, Electro-Magnetic A motor whose 

driving power is electricity. (See Motor, Electric.) 

Engraving, Acoustic Engraving by the human 

voice. 

In the Phonograph, Grapliophone, and Gramophone, a dia- 
phragm is set in vibration by the speaker's voice so that 
it cuts or engraves a record of its to-and-fro movements on a 
sheet of tin foil, on a cylinder of hardened wax, or on a 
specialty coated plate of metal or glass. This record is em- 
ployed in order to reproduce the speech. (See Phonograph.) 

Engraving, Electric ■ or Electro-Etching. 

— A method for electrically etching or engraving a metallic 
plate by covering it with wax, tracing the design on the wax 
so as to expose the metal, connecting it with the positive ter- 
minal of a battery, and placing it in a bath opposite another 
plate of metal. 

By the action of electrolysis the metal is dissolved from the 
exposed portions and deposited on the plate connected with 
the other terminal of the battery. (See Electrolysis.) 

By connecting the waxed plate to the negative terminal, 
the metal will be deposited on the exposed portions, thus pro- 
ducing the design in relief. This latter method is not, how- 
ever, apt to produce a sufficiently uniform deposit to enable 
the plate so formed to be used for printing from. 

Entropy. — In thermo-dynamics the non-available energy 
in any system. (Clausius and Mayer.) 



WORDS, TERMS AXD PHRASES. 250 

The available energy in any system. (Tait, Thomson, and 
Maxwell.) 

As will be noticed this term is used in entirely different and 
opposite senses by different scientific men. The latter sense 
is, perhaps, the one most generally taken. 

Heat energy is available for doing" useful external work 
only when the source of heat is hotter than surrounding- 
bodies, that is, when the heat is transferred from a hotter to a 
colder body. When all bodies acquire the same temperature 
no more external work can be done by them. In the various 
transformations of energy some of the energy is converted 
into heat, and this heat is gradually diffused through the 
universe and thus becomes non-available to man. There- 
fore, the entropy of our earth is decreasing-. 

"Entropy, in Thermodynamics," says Maxwell, "is a 
quantity relating to a body such that its increase or diminu- 
tion implies that heat has entered or left the body. The 
amount of heat which enters or leaves the body is measured 
by the product of the increase or diminution of entropy into 
the temperature at which it takes place." 

Entropy, Electric A term proposed by Maxwell 

in thermo-electric phenomena to include the doctrine of en- 
tropy in electric science. 

" When an electric current," says Maxwell, "passes from 
one metal to another heat is emitted or absorbed at the junc- 
tion of the metals. We should, therefore, suppose that the 
electric entropy has diminished or increased when the elec- 
tricity passes from one metal to the other, the electric entropy 
being different according to the nature of the medium in 
which the electricity is, and being affected by its temperature, 
stress, strain, etc." 

Equator, Geographical An imaginary great 

circle passing around the earth midway between its poles. 

Equator, Magnetic — The magnetic parallel, or 

circle on the earth's surface where a magnetic needle free to 
more stands horizontal. 



260 



A DICTIONARY OP ELECTRICAL 



i \ LL' / / 



An irregular line passing around the earth approximately 
midway between the earth's magnetic poles. (See Dip, Angle 
of.) 

Equator of Magnet.— A point midway between the poles 
of a bar magnet. 

This term was proposed by Dr. Gilbert. It is now almost 
entirely displaced by the term neutral point or points. 

Equipotential Surfaces.— Surfaces, all the points of 
which are at the same electric potential. (See Potential, 
Electric.) 

Electric surfaces perpendicular to the lines of electric force 
over which aquantity of electricity, considered as being con- 
centrated at a point, may be 
moved without doing work. (See 
Field, Electrostatic.) 

In electrostatics, equipotential 
surfaces correspond with a water 
level, over which a body may be 
moved horizontally against the 
force of gravity without doing 
any work. 

In the case of the charged in- 
sulated sphere, shown in the Fig. 
194, the equipotential surfaces, 
represented by the circles, are 
concentric. 

Equipotential Surfaces, Magnetic 

Surfaces surrounding thejpoles of a magnet, or system of mag- 
nets, where the magnetic potential is the same. (See Poten- 
tial, Magnetic.) 

Magnetic equipotential surfaces extend in a direction per- 
pendicular to the lines of magnetic force. (See Field, Mag- 
netic.) 

Therefore work is required in order to move a unit pole 




WORDS, TERMS AND PHRASES. 261 

across equipotential magnetic surfaces, because in so doing 
it cuts the lines of magnetic force. 

Equipotential surfaces, whether electric or magnetic, cannot 
intersect one another since their potential is the same at all 
points. 

Eqaivalciil, Chemical The quotient obtained 

by dividing the atomic weight of any elementary substance by 
its atomicity. (See Atomic Weight. Atomicity.) 

The chemical equivalent is different from the atomic weight. 
The atomic weight of gold is 190.0. but since in chemical com- 
bination one atom of gold is capable of combining with three 
atoms of hydrogen, the weight of the gold, equivalent to that 
of one atom of hydrogen is one-third of 190.0, or 05.5. 

Equivalent, Electro-Chemical.— A number represent- 
ing the weight of an elementary substance Liberated during 
electrolysis by the passage of one coulomb of electricity. (See 
Electrolysis. ( 'oulomb.) 

It may be determined experimentally that one coulomb of 
electricity expended electrolytically will liberate .0000105 
grammes of hydrogen. Therefore a current of one ampere, 
or one coulomb per second, will liberate .0000105 gramme of 
hydrogen per second. The number .0000105 is the electro- 
chemical equivalent of hydrogen. 

The electro-chemical equivalents of the other elements 
are obtained by multiplying tbe electro-chemical equiv- 
alent of hydrogen by the chemical equivalent of the sub- 
stance. 

Thus, the chemical equivalent of potassium is 39.1, therefore 
its electro-chemical equivalent is 39.1 x .0000105 = .00041055. 
By multiplying the strength of the current that passes by the 
electro-chemical equivalent of any substance., we obtain the 
weight of that substance liberated by electrolysis. 

The following Table of Electro-Chemical Equivalents is col^ 
lected from different authorities, mainly Hospitalier. 



262 



A DICTIONARY OF ELECTRICAL 



Electro- Chemical Eq uivalents. 






Names of Elements. 


5 

M 

2 

o 

< 


o 


a 

a' 
W 

'« 

o 

a 

.£3 
O 


J! 
g- 

|| 

£ So 
o> A 

V" 5 

o ?> ° 


!§ 

23 
S2 

O (D 

a a 

o— < 

£° • 

C] W <A 
" " fcl. 


M 

go 

•2 ^ 

S S • 

» £'£ 


Electro-positive. 
Hydrogen 


1. 

39.1 

23. 
196.6 
108. 

63. 

63. 
200. 
200. 
118. 
118. 

56. 

56. 

59. 

65. 
207. 

16. 
35.5 
127. 
80 
14. 


1 
1 
1 

3 
1 
2 
1 
2 

1 
4 
o 

4 
2 

2 
2 
2 

2 
1 
1 
1 
3 


1. 

39.1 

23. 

65.5 

108. 

31 5 

63. 
100. 
200. 

29 5 

59, 

14. 

28. 

29.5 

32.5 
103.5 

8. 

35.5 
127. 
80. 
4 3 


.0000105 
.0004105 
.0002415 
.0006875 
.0011340 

0003307 
.0006615 
.0010500 

0021 JOO 
.0003097 
.0006195 
. 0001470 
. 0002940 

0003097 

0003412 
.0010867 

.0000840 
.0003727 
.0013335 
.0008400 
. 0000490 


96,000 
2,455 
4,174 
1,466 

889 
3,079 
1,540 

960 

480 
3,254 
1,627 
6,857 
3,429 
3,254 
2,953 

928 


.0378 


Potassium 


1.4680 


Sodium 


.8694 


Gold.. 


2.4750 


Silver _. 

Copper (ic salts) 

Copper (ous salts) . ._ 

Mercury (ic salts) 

Mercury (ous salts).. 
Tin (ic salts) ... 


4.0824 
1.1900 
2.3800 
3.7800 
7.5600 
1.1149 


Tin (ous salts) 

Iron (ic salts).. 

Iron (ous salts). 

Nickel 


2.2298 

.5292 

1.0584 

1 . 1249 


Zinc 

Lead 


1 2283 
3.9041 


Electro-nega tive. 

Oxygen 

Chlorine 

Iodine .. 





Bromine . 




Nitrogen 









Equivalent of Heat, Heclianieal (See Me- 
chanical Equivalent of Heat.) 

Equivolt.— A term proposed by J. T. Sprague for the unit 
of electrical energy, applied especially to chemical decomposi- 
tion. 



WORDS, TERMS AND PHRASES. 2(33 

Sprague defines equivolt as follows : " The mechanical 
energy of one volt electro-motive force exerted under unit 
conditions through one equivalent of chemical action in 
grains." 

This term has not been generally accepted. (See Volt- 
Coulomb, or Joule.) 

Erg. — The unit of work, or the work done when unit force 
is overcome through unit distance. 

The work accomplished when a body is moved through a 
distance of one centimetre with the force of one dyne. (See 
Dyne.) 

The work done when a weight of one gramme is raised 
against gravity through a vertical height of one centimetre, 
is equal to 981 ergs, because the weight of one gramme is 
1 x 981 dynes, or 981 ergs. 

The dyne is the unit of force, or a force capable, after act- 
ing for one second, of giving a mass of one gramme a 
velocity of one centimetre per second. The weight of a body 
in dynes, or the force with which it gravitates, is equal to its 
mass in grammes, multiplied by the acceleration imparted to 
it in centimetres per second. For this latitude the accelera- 
tion is about 981 centimetres per second. 

Ergmcter. — An apparatus for measuring in ergs the work 
of an electric current. 

Erg-ten. — A term proposed for ten million ergs or 1 X 10 10 
- 10,000,000,000. 

In representing large numbers containing many ciphers the 
plan is often adopted of representing the number of ciphers 
that are to be added to a given number &3 T 10, with an exponent 
equal to the number of ciphers. Thus, 38 x 10 8 indicates that 
38 is to be followed by 8 ciphers, thus 3,800,000,000. 

A negative exponent, as 3 X 10- 8 represents the correspond- 
ing decimal thus, .00,000,003. 

1 erg X 10 10 , or 10,000,000,000 is called an erg-ten. 1 X 10 6 



204 A DICTIONARY OF ELECTRICAL 

= an erg-six. These terms are not in general use. Ten 
meg-ergs is a preferable phrase to an erg-ten. (See Meg-erg.) 

Escape, Electric A term sometimes employed 

to indicate the loss of charge on an insulated conductor. (See 
Leakage, Electric.) 

Etching, Electric (Sec Engraving, Electric.) 

Ether. — The tenuous, highly elastic fluid that is assumed 
to fill all space, and by vibrations or waves in which light 
and heat are transmitted. 

Although the existence of the ether is assumed in order to 
explain certain phenomena, its actual existence is very 
generally credited by scientific men, and, in reality, proofs are 
not wanting to fairly establish its existence. 

Light and heat are believed to be due to transverse vibra- 
tions in the ether. Magnetism appears to be due to whirls or 
whirl-pools, and an electric current is believed by some to be 
due to ether set in motion by differences in the ether pres- 
sures. 

It is not correct to regard the luminiferous ether as possess- 
ing no weight, or as being imponderable. Maxwell estimates its 
936 

density as 1,000,000,000,000,000,000,000 that of water * xt 

is very readily moved or set into vibration, its rigidity being 

estimated at about — — that of steel. 

1,000,000,000 

According to the speculations of some physicists the ether 
is not discontinuous or granular, but is similar to what might 
be regarded as an almost impalpable jelly. 

Eudiometer. — A Voltameter in which separate gradu- 
ated vessels are provided for the reception and measurement 
of the gaseous products evolved during electrolysis. (See 
Voltameter.) 

In all cases electrodes must be used which do not enter into 
combination with the evolved gaseous products. In the 
case of oxygen and hydrogen, platinum is generally used. 



WORDS, TERMS AND PHRASES. 



265 



A form of eudiometer is shown in Fig-. 195. Two separate 
glass vessels provided at the top with stop cocks, and open at 
their lower ends, rest in a vessel of water A, over platinum 
electrodes, connected electrically with binding posts K, K. 
Both vessels are tilled with 
water slightly acidulated with 
sulphuric acid, and, when 
connected with a battery of 
sufficient electro-motive force, 
(not less than 1.45 volts), elec- 
trolysis takes place, and hy- 
drogen gas collects in the 
vessel over the platinum elec- 
trode connected with the neg- 
ative battery terminal, and 
oxygen in that over the one 
connected with the positive 
battery terminal. The volume 
of the hydrogen is about twice 
as great as that of the oxygen. 
(See Water, Electrolysis of .) 

E v a |> o r a 1 i o n . — The 
< hange from the liquid to the 
vaporous state. 

Wet clothes exposed to the 
air are dried by the evapora- 
tion of the water. 

Evaporation is greater : 

(1) The more extended the 
surface exposed. 

(2) The higher the temperature of the air. 

(3) The dryer the air, or the smaller the quantity of vapor 
already in it. 

(4) The stronger the wind. 

(5) The smaller the pressure of the air. 




Fig, 1V5. 



266 A DICTIONARY OF ELECTRICAL 

Evaporation, Electrification by Electrifica- 
tion resulting from the condensation of a mass of vapor. 

The free electricity of the atmosphere is believed by some 
to be due to the condensation of the vapor of the air that 
results in rain, hail, clouds, etc. It is probable, however, 
that the true effect of condensation is mainly limited to the 
increase of a feeble electrification already possessed by the 
air or its contained vapor. The small difference of potential 
of the exceedingly small drops of water in clouds, is enor- 
mously increased by the union or coalescing- of many thous- 
ands of such drops into a single rain drop. (See AtmospJieric 
Electricity.) 

Exchange, Telephonic System of —A com- 
bination of circuits, switches and other devices, by means of 
which any one of a number of subscribers connected with a 
telephonic circuit, or a neighboring telephonic circuit or cir- 
cuits, may be placed in electrical communication with any 
other subscriber connected with such circuit or circuits. 

A telephone exchange consists essentially of a multiple 
switch-board, or a number of multiple switch-boards, fur- 
nished with spring-jacks, annunciator drops, and suitable con- 
necting cords. A call bell, or bells, is also provided. The 
annunciator drops are often omitted. (See Board, Multiple 
Sivitch.) 

Excitability, Electric of tferve or Muscular 

Fibre. — The effect produced by an electric current in stimu- 
lating the nerve of a living animal or producing an involun- 
tary contraction of a muscle. 

Du Bois-Reymond has shown that these effects depend ; 

(1) On the strength of the current employed, and that they 
occur only when the current begins to flow, and when it 
ceases flowing, or, when the electrodes first touch the nerves, 
and when they are separated from it. Subsequent investiga- 
tion have shown that this is true only for the frogs nerves, 



WORDS, TERMS AND PHRASES. 267 

and is true for the human nerves only in the case of moderate 
currents, strong' currents producing- tetanus. 

(2) On the rapidity with which the current used readies its 
maximum value, that is, on the rapidity of change of current 
density. (See Current Density.) 

Excitability, Faradic Muscular or nervous 

excitability following the employment of the rapidly intermitt- 
ent current produced by induction coils. (See Induction Coils.) 

Faradic excitability is different from galvanic excitability, 
produced by means of a continuous voltaic current. 

Excitation, Electro Muscular (See Electro 

M use u la r Excitation.) 

Exciter of Field. — In a separately excited dynamo- 
electric machine, the dynamo-electric machine, voltaic bat- 
tery, or other electric source employed to produce the field of 
the field magnets. (See Dynmuo-Electric Machines.) 

Execution, Electric Causing the death of a 

criminal, in cases of capital punishment, by means of the 
electric current. 

Electric execution has been adopted by the State of New 
York, in accordance with the following law : 

"The Court shall sentence the prisoner to death within a 
certain week, naming no day or hour, and not more than 
eight nor less than five weeks from the day of sentence. The 
execution must take place in the State prison to which con- 
victed felons are sent by the court, and the executioner must 
be the agent and warden of the prison."' 

"No newspaper may print any details of the execution, 
which is to be inflicted by electricity. A current of electricity 
is to be caused to pass through the body of the condemned of 
sufficient intensity to kill him, and the application is to be 
continued until he is dead." 

Exhaustion, or Prostration Electric— (See 

Sun Stroke, Electric.) 



208 A DICTIONARY OF ELECTRICAL 

I x 1 1 . Million of Voltaic Cell.— The condition of a 
voltaic cell in which, on account of having all its active elec- 
trolyte decomposed, or its positive plate dissolved, it will 
furnish no difference of potential and therefore no current. 

An exhausted secondary cell is revivified or charged, by the 
passage through it of a charging current. 

A primary cell is revivified by the addition of fresh electro- 
lyte or battery liquid, or a new positive plate. 

Expansion, Electric The increase in vol- 
ume produced in a body on giving- such body an electric 
charge. 

A Leyden jar increases in volume when a charge is im- 
parted to it. This result is due to an expansion of the glass 
due to the electric charge. According to Quincke, some sub- 
stances, such as resinous or oily bodies, manifest a contrac- 
tion <>f volume on the reception of an electric charge. 
Expansion Join I*. — (See Joints, Expansion.) 
Explo<lcr, Electric — — A small magneto- 
electric machine used to produce the currents of high electro- 
mo-tive force, employed in the direct firing of blasts. 

Explorer, Electric ■ — An apparatus oper- 
ated by means of induced currents, and employed forthe pur- 
pose of locating ballets or other foreign metallic; substances 
in the human body. (See Balance, Induction, Hughes.) 

Explorer, magnetic — A small, flat coil of in- 
sulated wire, used in the circuit of a telephone to determine 
the position and extent of the magnetic leakage of a, dynamo- 
eli'i trie machine or other similar apparatus. (See Magneto- 
phone.) 
Extension Call-Bell.— (See Bell, Extension Call.) 
Extra Current*. — Currents produced in a circuit, by 
the induction of the current on itself, on the opening or cloning 
of a circuit. (See Currents, Extra.) 
Eye, Selenium —(See Selenium Eye.) 



WORDS. TERMS AXD PHRASES. 



Facsimile Telegraphy, or Pantelegrapby.— The 

telegraphic transmission of fac-simile copies of drawings or 
designs. 

In a system of fac-simile telegraphy, a design placed at one 
end of a telegraphic line is automatically reproduced by elec- 
tricity at the other end of the line. (See Telegraphy, Fac- 
simile.) 

Farad.— The unit of electric capacity. 

As in gases, a quart vessel will hold a quart of gas under 
unit pressure of one atmosphere, so, in electricity, a conduc- 
tor or condenser, whose capacity is one farad, will hold a 
quantity of electricity equal to one- coulomb, when under an 
electro-motive force o!' one volt. 

It may cause some perplexity to the student to understand 
why there should be in electricity 
one unit of capacity to represent 
the size of the vessel or conductor, 
and another to represent the 
amount or quantity of electricity 
required to fill such vessel. But, 
like a gas, electricity acts as if it 
were very compressible, so that ™ 
the quantity required lo fill any Mg. 196. 

condenser will depend on the electro-motive force under which 
it is put into the conductor or condenser. 

A farad is such a capacity of a conductor or condenser that 
one coulomb of electricity is required to produce in it a differ- 
ence of potential of one volt. 

For purposes of measurement, capacities of conductors are 
compared with those of condensers whose capacities are 
known in microfarads, or fractions thereof. The microfarad, 
1 




or the 1,000,000 
size of a farad. 



of a farad, is used hecause of the very great 



Fig. 19(5, shows an elevation and Fig. 197 a plan of the form 



270 



A DICTIONARY OP ELECTRICAL 



often given to a standardized condenser or microfarad. The 
condenser is charged by connecting' the terminals of the elec- 
tric source to the binding posts N and N. It is discharged by 
means of the plug key P', that 
connects the brass pieces A and 
B, when pushed firmly into the 
conical space between them. 

The condenser is made by plac- 
ing sheets of tin foil between 
sheets of oiled silk or mica in the 
box, and connecting the alter- 
nate sheets to one of the brass 
pieces B, and the other set to the 
piece A, as will be better under- 
Fig. 197. stood from an inspection of Fig. 

198. A condenser of a microfarad capacity will contain about 
3,000 square inches of tin foil. 

Condensers are generally made of the capacity of the i of a 
microfarad. Sometimes, however, they are made so that 
either all or part of the condenser may be employed, by the 
insertion of the different plug keys. 
The form of condenser, shown 
ready division into five differ- 




ent values, viz.: .05, .05, .2, 
.2, and .5 microfarad. 

Faradic Apparatus, 
II a jj ii i' I o A 

small magneto-electric ma- 
chine employed in electro 
therapeutics for producing 
faradic currents. 

These machines consist es- 



Fig. 199 is capable of 
b 



Fig. 198. 



sentially of a coil of wire wrapped on an armature core rotated 
before the poles of permanent magnets. No commutator is em- 
ployed, since it is desired to obtain rapidly alternating currents. 



WORDS, TERMS AXD PHRASES. 



271 



Faradic Brush.— (See Brush, Faradic) 

Faraclic Current. — In electro therapeutics the current 
produced by an induction coil. 

A rapidly alternating current, as distinguished from a uni- 
form voltaic current. 

A voltaic current that is rapidly alternated by means of 
any suitable key or switch is sometimes called a voltaic al- 
ternative. The discharge from a Holtz machine is sometimes 
called a Franklinic Current. 

Faradic Induction Apparatus.— An induction coil 
apparatus for producing faradic currents. 

A voltaic battery is connected with the primary of an induc- 
tion coil, and its cur- 
rent rapidly broken 
by an a u torn a t i c 
break, or by a hand 
break. The alter- 
nating or faradic 
currents thus pro- 
duced in the second- 
ary coils are used 
for electro therapeu- 
tic purposes. (See 
Induction Coil.) 

Faradic induction 
apparatus are made 
in a great variety of 
forms. They all operate, however, on essentially the same 
principles. 

Faradic Machines.— Machines for producing Faradic 
currents. 

These are of two varieties, viz. : magneto-faradic apparatus, 
and simple induction apparatus. 

Faradization. — In electro therapeutics, the effects pro- 




Fig. 199. 



272 A DICTIONARY OF ELECTRICAL 

duced on the nerves or muscles b} r the use of a farad ic cur- 
rent, in order to distinguish such effects from galvanization 
or those produced by a voltaic current. 

Fahrenheit's Thermometer Scale.— A thermometer 
scale in which the length of the thermometer tube between 
the melting point of ice and the boiling- point of water is 
divided into 180 equal parts called degrees. 

On Fahrenheit's scale, water freezes at 32° F. and boils at 
212° F. Degrees of this thermo-metric scale are represented 
by an F. (See Centigrade Thermometer Scale.) 

False Pole, Magnetic A term proposed by 

Mascait and Joubert, to designate the extra magnetic poles of 
the earth, or places acting as magnetic poles, in addition to 
the two poles near the earth's geographical poles. 

According to these authorities, the earth possesses two 
magnetic poles only, viz., a negative pole in the Northern 
Hemisphere, and a, positive pole in the Southern Hemisphere. 
The additional poles, are called by them the false magnetic 
poles. 

Faults. — Accidential leaks in a circuit caused by ground 
contacts or crosses. (See Cross Contacts.) 
Faults are of three kinds, viz. : 

(1) Disconnections. (See Disconnections.) 

(2) Earths. (See Earths.) 

(3) Contacts. (See Contacts.) 

Various methods are employed for detecting and localizing 
faults, for the explanation of which reference should be had 
to standard electrical works. 

Faults, Localization of — (See Localization of 

Faults.) 

Ferro-Magnetic Substances. — A term proposed in 
place of paramagnetic, for substances that are magnetic, 
after the manner of iron. (See Paramagnetic.) 



WORDS, TERMS AND PHRASES. 



273 



Paramagnetic is the preferable term. The use of the 
term ferromagnetic is both unnecessary and unwarranted. 

Fibre-Suspension. — The suspension of a needle by 
means of a fibre. 

Fibre suspension may be effected by means of a single 
fibre or thread, or by two parallel threads, which is called 
bi-filar suspension. (See Suspension, Fibre. Suspension, Bi- 
filar.) 

(See Vulcanized Fibre.) 



Fibre, Vulcanized - 
Field, Electrostatic 

influence surround- 
ing a charged body. 

Electrostatic at- 
tractions or repul- 
sions take place 
along certain lines 
called lines of elec- 
tro st at ic force. 
These lines of force 
produce a field 
called an electro- 
static field. Elec- 
tric level or poten- 
tial is measured 
along these lines, 
just as gravitation Fi 9- 20 °- 

levels are measured with a plumb line along the lines of grav- 
itation force. (See Potential) 

Work is done when a body is moved along the lines of elec- 
trostatic force in a direction from an oppositely charged body, 
or towards a similarly charged body, just as work is done 
against gravity, when a body is moved along the lines of 
gravitation force, away from the earth's centre, or vertically 
upwards. 




274 



A DICTIONARY OF ELECTRICAL 



Field, Intensity of (See Field, Magnetic. Field, 

Electrostatic Field, Electro Magnetic.) 

Field, magnetic The region of magnetic influ- 
ence surrounding the poles of a magnet. 

Strictly speaking- a magnetic field is a place where a mag- 
netic needle, if free to move, will take up a definite posi- 
tion. 

Magnetic attractions and repulsions are assumed to take 
place along certain lines called lines of magnetic force. Their 

direction in any plane 
of a magnetic field, maj r 
be shown by sprinkling- 
iron filings over a sheet 
of paper field in a hori- 
zontal position to a 
magnet pole inclined to 
the paper in the desired 
plane and then gently 
tapping the paper. 

These are sometimes 

called magnetic figures. 

The lines of force thus 

shown will appear from 

an inspection of Fig. 200, 

taken in a plane join 
Fig. 201. . j, , ! - 

ing the two poles of a 

straight bar magnet, and Fig. 201, taken in a plane at right 

angles to the north pole of a straight bar magnet. 

In Fig. 200, the repulsion of the lines of force at either pole 
is shown by the radiation of the chains of magnetized iron 
particles. The mutual attraction of unlike polarities is shown 
by the curved lines. 

In Fig. 201, the repulsion of the similarly magnetized chains 
is clearly shown. 

Lines of magnetic force are assumed to pass out from the 




WORDS, TERMS AXP PHRASES. 



275 



north polo and- inte the south pole. This is called thedirec- 
tion of the lines of force. 

The density of a magnetic field is directly proportional to 
the number of linos of force per unit of area of cross section. 

A single line of force, or a unit line of force, is such an in- 
tensity of field as exists in each square centimetre of cross 
section of a unit magnetic field. 

A magnetic field is uniform, or possesses uniform intensity , 
when it possesses the same number of lines of force per square 
centimetre of area of cross section. 



Field, Magnetic* 

The magnetic field 
surrounding a circuit 
through which an 
electric current is 

11 owing - . 

An fleet lie current 
produces a magnetic 
field. This was dis- 
covered by Oersted, 
m 1819, and may be 
shown by sprinkling 
iron filings on a sheet 
of paper, placed on 
t he wire or conductor 
conveying the cur- 
rent, at right angles 



of an Electric Current.— 




Fig. 202. 

to the direction in which the current is passing. Here the 
lines of force appear as concentric circles, around the con- 
ductor, as shown in Fig. 202. Their direction, as regards the 
length of the conductor, is shown in Fig. 203. The electric 
current sets up these magnetic whirls around the conductor 
on its passage through it. 

The direction of the lines of magnetic force produced by an 
electric current, and hence its magnetic 'polarity, depends on 



276 



A DICTIONARY OP ELECTRICAL 



the direction in which the electric cut rent flows. This direc- 
tion may be remembered as follows: If the current flows to- 
1 wards the observer, the direction of the lines 

of magnet ic force is opposite to that of the hands 
of a watch, as shown in Fig. 204. 

It is from the direction of the lines of force 
that the polarity of a helix carrying a current 
is deduced. (See Magnetic Solenoid. Electro- 
Magnet.) 

A magnetic field possesses the following prop- 
erties, viz. : 

(1) All magnetizable bodies are magnetized 
when brought into a magnetic field. (See In- 
duction, Magnetic) 

(2) Conductors moved through a magnetic 
field so as to cut its lines of force, have differ- 
ences of potent ial generated in them at different 
points, and if these points be connected by a 
conductor, an electric cm-rent is produced. (See 
Induction, Electro-Magnetic.) 

Figure of merit of Galvanometer.— The reciprocal 
of the current required to 
produce a deflection of the 
g a 1 v a n o mete r needle 
through one degree of the 
scale. 

The smaller the current 
required to produce a de- 
flection of one degree, the 
greater the figure of merit, 
or the greater the sensi- 
tiveness of the galvano- 
meter. 

Figures, Electric — 




Fk/. 203. 




Fig. 20U. 

Licliteiifoerg's Oust 
Figures. — Figures produced by writing on a sheet of shellac 



WORDS, TERMS AND PHRASES. 



277 



with a knob of a Leyden jar, and then sprinkling over it a 
mixture of powdered sulphur and red lead, which have been 
previously mixed together, and are so rendered, respectively, 
negative and positive. 

The red lead collects on the negative parts of the shellac 
surface, and the sulphur on the positive parts, in curious 
figures, known as Lichtenbenfs Dust Figures, one of which is 
shown in. Fig. 205. 

These figures show very clearly that an electric charge fends 
to creep irregularly over the surface of an insulating substance 



Figures, Electric 

Faint figures of 
condensed vapor 
produced by elec- 
trifying a c i n , 
p 1 a c i Q g it mo- 
mentarily on the 
surface of a sheet 
of clean, dry 
glass, and then 
breathing gently 
on the spot where 
the coin was 
placed. 

The moisture 
collects on the 
electrilied por- 
tions and forms a 



or Breath Figure*.— 




Fig. S0& 
fairly distinct imaire of the coin. 



Figures, Magnetic 



A name, sometimes ap- 



plied toth 



•oupi 



>f iron filings on a sheet of paper held in 



a magnetic held. (.See Field. Magnetic.) 

Filament. — A slender thread or Jibre. 
The term is applied generally to threads or fibres varying 
considerably in diameter. 



278 A DICTIONARY OF ELECTRICAL 

Filament of Incandescent Electric Lamp.— A term 

now generally applied to the incandescing- conductor of an 
incandescent electric lamp, whether the same be of very small 
cross section, or of comparatively large cross section. 

The term filament is properly applied to a conductor con- 
taining fibres or filaments extending in the general direction 
of the length of the incandescing conductor. Such a con- 
ductor is made of carbonizable fibrous material, cut or shaped 
prior to carbonization, so as to have the fibres extending with 
their greatest length in the direction of length of the filament. 

Filament, Magnetic — A chain or thread of 

magnetized particles. 

This is sometimes called a uniform magnetic filament. 

A bar-magnet possesses but two free poles, which when 
broken at its neutral point or equat or will develop free poles at 
the broken ends. This is explained by considering the magnet 
to be composed of a number of separate particles, separately 
magnetized. A single chain or filament of such particles is 
called a magnetic filament. (See Neutral Point of a Magnet. 
Magnetism, Hughes' Theory of.) 

Fire Alarm, Electric A system for telegraph- 
ically sending an alarm of fire from stations in different 
portions of a district to the engine houses. (See Alarm, Elec- 
tric, Fire.) 

Such alarms are automatic when the alarm is sounded by 
the completion of the circuits by means of a thermostat. (See 
Thermostat.) 

Fire Extinguisher, Electric A thermo- 
stat, or a mercury contact, which automatically completes the 
circuit and turns on a water supply for extinguishing a fire, 
on a certain predetermined increase of temperature. 

Fi§lies, Electric (See Animal Electricity. Eel, 

Electric.) 



WORDS, TERMS AND PHRASES. 27\) 



Flashing of Carbons, Process for the 



— A process for improving- the electrical uniformity of the 
carbon conductors employed in incandescent lighting, by the 
deposition of carbon in their pores, and over their surfaces at 
those places where the electric resistance is comparatively 
great. 

The carbon conductor is placed in a vessel usually filled with 
the vapor of a hydro-carbon liquid called rhigolene, or any other 
readily decomposable hydro-carbon liquid, and gradually 
raised to electrical incandescence by the passage through it of 
an electric current. A decomposition of the hydro-carbon 
vapor occurs, the carbon resulting therefrom being- deposited 
in and on the conductor. If the current is gradually increased, 
those parts of the conductor which are first rendered incandes- 
cent, that is in those parts where the resistance is the highest, 
and practically those parts only, receive the deposits of carbon. 
As the current gradually increases, other portions become 
successively incandescent and receive a deposit of carbon, 
until at last the filament glows with a uniform brilliancy, in- 
dicative of its electric homogeneity. 

A carbon whose resistance varies considerably at different 
parts could not be successfully employed in an incandescent 
lamp, since if heated by a current sufficiently great to render 
the points of comparatively small resistance satisfactorily in- 
candescent, the temperature of the points of high resistance 
would be such as to lower the life of the lamp, while if only 
those portions were safely heated, the lamp would not be 
economical. The flashing process is therefore of very great 
value in the manufacture of an incandescent lamp. 

Flashing of Dynamo Electric Machine.— A name 
given to long, flashing sparks at the commutator, usually due 
to the short circuiting- of the external circuit at the commu- 
tator. 

Floating Battery, De la Rive's A floating 

voltaic cell, the terminals of which are connected with a coil 



280 



A DICTIONARY OF ELECTRICAL 



of insulated wire, employed to show the attractions and re- 
pulsions between magnets and movable electric circuits. 

The cell, shown in Fig. 206, consists of a voltaic couple of 
zinc and copper, the terminals of which are connected to the 
circular coil of insulated wire, as shown, and the whole floated 
by means of a cork, in a vessel containing- dilute sulphuric 
acid. 

When the current flows through the coil in the direction 
shown by the arrows, the approach of the N-seeking pole of a 
magnet will cause the cell to be attracted or to move to- 
wards the magnet pole, since the south face or end of the coil 
is nearer the north pole of the magnet. If the other end were 

nearer, repulsion would occur, 
the cell turning around until 
the south face is nearer the 
magnet, when attraction oc- 
curs. 

Flow. — In hydraulics, the 
quantity of water or other 
fluid which escapes from an 
orifice in a containing vessel 
in a given time. 




Flow 



Fig. 206. 

Direction of Cm 



•ent- 



— The direc- 



tion the current is assumed to take, i. e., from the positive 
pole of the source through the circuit to the negative pole of 
the source. 

The electricity is assumed to come out of the source at its 
positive pole, and to return or flow back into the source at its 
negative pole. (See Current, Direction of.) 

Flow of Line* of Electrostatic Force. — A mathe- 
matical conception in which the phenomena of electricity are 
compared with the similar phenomena of heat. 

In heat no flow of heat occurs over isothermal surfaces, or 
surfaces at the same temperature. Over different isothermal 



WORDS, TERMS AND PHRASES. 281 

surfaces the flow will vary with the power of heat conduc- 
tion. In electricity no flow occurs over equipotential sur- 
faces. Specific Inductive Capacity corresponds to heat con- 
ductivity, and the lines of force to the lines of heat conduction. 
(See Capacity, Specific Inductive.) 

FIuore§cence. — A property, possessed by certain solid or 
liquid substances of becoming self luminous while exposed to 
the light. 

Canary glass, or glass colored yellow by oxide of uranium, 
and a solution of sulphate of quinine, possess fluorescent prop- 
erties. The path of a pencil of light brought to a focus in 
either of these substances is rendered visible, by the particles 
lying in this path becoming self luminous. 

The path of a beam of light, entering the dusty air of a 
darkened chamber, is visible from the light being diffused or 
scattered in all directions by the floating dust particles. So 
in a tiuoreseent substance the path of the light is also ren- 
dered visible by the particles which lie in its path, throwing 
out light in all directions. There is, however, this difference, 
that in the case of the dust particles the light which conies 
directly from the beam is reflected, while in the case of the 
fluorescent body the light is from the particles themselves, 
which are set into vibrations by the light that is passing 
through, and has been absorbed by their mass. 

Fluorescence is, therefore, a variety of phosphorescence. 
(See Phosphorescence.) 

Flush Boxes. — A box or space, flush with the surface of 
a road bed, provided in a system of underground wires or 
conduits, to facilitate the introduction of the conductors into 
the conduit, or for the examination of the conductors. 

Flyer, Electrie Electric Fly, or Electric Re- 
action Wheel. — A wheel arranged so as to be set into rota- 
tion by the escape of convection streams from its points when 
placed on a charged conductor. 



38S 



A DICTIONARY OF ELECTRICAL 



A wheel formed of light radial arms P, P, shaped as shown 
in Fig. 207, and capable of rotation on the vertical axis A, is 
set into rapid rotation when connected with the prime conduc- 
tor of a machine, through the convection streams of air parti- 
cles which are shot off from the points or extremities of the 
radial arm. The wheel is driven by the reaction of these 
streams in a direction opposite to that of their escape. (See 
Discharge, Convectivc.) 

Focus. — The point in front or back of a lens, or mirror, 
where the rays of light meet. (See 
Achromatic Lens.) 

Fog, Electric Dense fogs 

which occur on rare occasions when 
there is an unusual quantity of free 
electricity in the atmosphere. 

During these electric fogs the free 
electricity of the atmosphere changes 
its polarity at frequent intervals. 

Following Horns of Dynamo- 
Electric Machine. — (See Horns, 
Folio iv ing , of Dynamo- Electric 
Machine.) 
Foot Candle— (See Candle, Foot.) 
Foot-Found.— A unit of work. (See Work.) 
The amount of work required to raise one pound vertically 
through a distance of one foot. 

The same amonnt of work is done by raising one pound 
through a vertical distance of three feet, or three pounds 
through a vertical distance of one foot, viz., three foot- 
pounds. 

Apart from air friction, the amount of work done in raising 
one pound through one foot, viz., one foot-pound, is the same 
whether this work be done in one second, or in one clay. The 
power, however, or the rate of doing work is very different in 
the two cases. (See Power.) 




Fig. 207. 



AVORDS, TERMS AND PHRASES. 283 

For another unit of work, see the Erg. 

Force. — Any cause which changes the condition of rest or 
motion of a body. 

Force, Centrifugal (See Centrifugal Force.) 

Force, Coercive or Cocrcif ive or Magnetic 

Retentivitv. — The power of resisting magnetization or de- 
magnitization. (See Coercive Force.) 

Force, Composition of (See Components.) 

Force, Electrostatic The force producing the 

attractions or repulsions of charged bodies. 

Force, Lines of Electrostatic (Sec Field, 

Fleetro-Stotic.) 

Force, Eincs of Magnetic (See Field, Mag- 
netic.) 

Force, Magnetic The force which causes the at- 
tractions or repulsions of magnet poles. (Sec Magnetic Force. ) 

Force, Resolution of —(See Resultants.) 

Force, Tubes of or Tubes of Induction.— 

Tubes bounded by lines of electrostatic or magnetic force. 

Lines of force never intersect one another. Hence a tube of 
force may be regarded as containing the same number of lines 
of force at any and every cross section. 

Tubes of electrostatic force always terminate against equal 
quantities of positive and negative electricity respectively. 
They terminate when they meet a conducting surface. 

The term tubes of force is somewhat misleading, since such 
so-called tubes are in general cones rather than tubes. 

Force, Unit of ■ or Dyne— A force, which acting 

for one second, on a mass of one gramme, will give it a ve- 
locity of one centimetre per second. (See Dyne.) 

Forces, Parallelogram of —A parallelogram 

constructed about the two lines that represent the direction 
and intensity with which two forces are simultaneously acting 



284 A DICTIONARY OF ELECTRICAL 

on a body, in order to determine the direction and intensity 
of the resultant force with which it moves. 

If the two forces A C and A B, Fig. 208, simultaneously 
act in the direction of the arrows on a body at A, the direction 
and intensity of the resultant, A D, is determined by draw- 
ing D C and B D, parallel respectively to A B, and A C. 
The diagonal A D, of the parallelogram A C D B, thus pro- 
duced, gives this resultant. (See Components.) 

Forming Plates of Secondary or Storage Cells.— 

Obtaining a thick coating of lead monoxide on the plates of 
a storage cell, by repeatedly sending the charging current 
through the cell alternately in opposite directions. (See 
Storage of Electricity.) 

I D ^ Forninlie. — Mathematical expressions 
B f"" —~pfr f or S ome general rule or principle. 

^s^ Formulae are of great assistance in 

^^ science in expressing the relations wbicli 

A ' exist between certain forces or values, 

Fig. 208. am j ^ ne e ff ec t s t] ia t result from their oper- 

ation, since they enable us to express these relations in clear 
and concise forms. 

Thus, in the formulation of Ohm's law, 

E 
C = — , 
R 
we see that the current C, in any circuit is equal to the elec- 
tro-motive force E, divided by the resistance R. Again, we 
see that the current is directly proportional to the electro- 
motive force, and inversely proportional to the resistance. 

Formulae are usually written in the form of an equation, 
and therefore contain the sign of equality or =. 

Formulae, Photometric —(See Photometric 

Formulae.) 

Foucault Currents, Eddy Currents, Parasitical 
Currents, Local Action,— (See Currents, Eddy.) 



WORDS, TERMS AND PHRASES. 



285 



Fraiiklinie Electricity. — A term, sometimes employed 
in electro therapeutics, for the electricity produced by a fric- 
tional or an electrostatic induction machine. 

Free Charge, Free Electricity.— (.See Charge, Bound 
and Free.) 

Frictioiial Electricity. — Electricity produced by fric- 
tion. 

This term as formerly employed to indicate static charges 
as distinguished from currents, is gradually falling into dis- 
use, and the frictional electric 
machines, are being generally 
replaced by continuous induc- 
tion machines, like those of 
Holtz, Topler-Hdltz, orWims- 
hurst. 

Frog, Qalvanoscopic 

The hind legs of a re- 
cently killed frog, employed 
as an electroscope or galvano- 
scope by sending an electric 
current from the nerves to 
the muscles. (See Electro- 
scope. ) 

In 1786, Luigi Galvani, made 
the observation that when the Fig - ~ 09 - 

legs of a recently killed frog were touched by a metallic con- 
ductor connecting the nerves with the muscles, the legs were 
convulsed as though alive. He repeated this experiment, 
and found the movements were more pronounced when two 
dissimilar metals, such as iron and copper, were employed in 
the manner shown in Fig. 209. 

This classic experiment created intense excitement in the 
scientific world, and Galvani at first believed that he had dis- 
covered the true vital fluid of the animal, but afterwards 




286 A DICTIONARY OF ELECTRICAL 

recognized it as electricity, which he believed to be obtained 
from the body of the animal. Volta, claimed that the move- 
ments were due to electricity caused by the contact of dissi- 
milar metals, and thus produced his famous voltaiepile. (See 
Pile, Voltaic.) 

Fulgurite. — A tube of vitrified sand, believed to be formed 
by a bolt of lightning-. 

The fulgurite consists of an irregular shaped tube of glass 
formed of sand which has been melted by the electric dis- 
charge. 

Fulminate.— The name of a class of highly explosive 
compounds. 

Fulminating gold, silver, and mercury, are highly explos- 
ive substances. Fulminates are employed on percussion caps. 

Functions, Trigonometric (See Trigonomet- 
ric Functions.) 

Fundamental Units. — (See Units, Fundamental.) 

Furnace, Electric A furnace in which heat, 

generated electrically, is employed for the purpose of effect- 
ing difficult fusions, for the extraction of metals from their 
ores, or for other metallurgical operations. 

In electric furnaces the heat is derived either from electric 
incandescence, or from the voltaic arc. The latter form is 
frequently adopted. 

The substance to be treated is exposed directly to the vol- 
taic arc. In some forms of furnace the crushed ore is per- 
mitted to fall through the arc, and the melted matter received 
in a suitable vessel, in which the separation of the substances 
so formed, is afterwards completed. In other forms of furnace, 
the ore is placed between two electrodes of carbon or other 
refractory substances, between which a powerful current is 
passed. In the Cowles furnace, when aluminium is reduced, 
molten copper forms an alloy with the aluminium as soon as 
it is separated. 



WORDS, TERMS AND PHRASES. 



287 



Very numerous applications of electricity to furnace opera- 
tions have boon made, for details of which, standard works 
should be consulted. 

Fuse, Electric A device for electrically igniting 

a charge of powder. 

Electric fuses are employed both in blasting operations and 
for firing cannon. 

Electric fuses are operated either by means of the direct 
spark, or by the incandescence of a thin wire, 
placed in the circuit. They are therefore either 
high tension, or low tension fuses. 

The advantages of an electric fuse consist in the 
fact that its use permits the simultaneous firing 
of a number of charges in a mining operation, thus 
obtaining a greater effect from the explosion. A 
fulminate of mercury is frequently employed in 
connection with some forms of electric fuses. 

A form of fuse in which the ignition is effected 
by the electric spark is shown in Fig. 210, and is 
known as Strathcnns fuse. The spark passes 
through a break A B, in the insulated leads D. 
Since gunpowder is not readily ignited by an 
electric spark, a peculiar priming material is em- 
ployed at A B, in the place of ordinary powder. 

Fu§c, Safety Safety Strip, or Safety 

Plug. — A strip, plate, or bar of lead or some 
readily fusible alloy, that automatically breaks Fi V- ~ 10 - 
the circuit in which it is placed on the passage of a current 
of sufficient power to fuse such strip, plate, or bar, when 
such current would endanger the safety of other parts of 
the circuit. 

Safety fuses are made of alloys of lead, and are placed in 
boxes, lined with non-combustible material, in order to pre- 
vent fires from the molten metal. Fig. 211, shows a fusible 
strip F, connected with leads L, L. Safet}' fuses are placed 



288 



A DICTIONARY OP ELECTRICAL 



on all branch circuits, and are made of sizes proportionate to 
the number of lamps they guard. 

Since incandescent lamps are generally connected with the 
circuit in multiple-arc, or in multiple-series, one or more of 
the circuits can be opened by the fusion of the plug with- 
out interfering with the continuity of the rest of the circuit. 
In series circuits, however, such as arc light circuits, when a 
lamp is cut out, a short circuit or path around it must be pro- 
vided to avoid the extinguishing of the rest of the lights. 




Fig. 211. 

Galvanic Battery — Two or more voltaic cells so ar- 
ranged as to form a single source. (See Battery, Voltaic.) 

Galvanic Cell.— (See Cell, Voltaic.) 
Galvanic Circle. — (See Circle, Galvanic.) 

Galvanic Circuit. — A term sometimes employed instead 
of the term voltaic circuit. The term galvanic in place of 
voltaic is unwarranted by the facts of electric science. ( See 
Circuit, Voltaic.) 

Gal vani thought he had discovered the vital fluid of animals . 
Volta first pointed out the true explanation of the phenomena 
observed in Galvani's frog, and devised the means for produc- 
ing electricity in this manner. The terms voltaic battery, cell, 
circuit, etc., are therefore preferable. 



WORDS, TERMS AND PHRASES. 289 

Galvanic Polarization. — A term sometimes applied to 
the polarization of a voltaic cell. (See Polarization of Vol- 
taic Cell.) 

Galvanism. — A term sometimes employed to express the 
effects produced by voltaic electricity. 

Galvanization. — In electro therapeutics the effects pro- 
duced on nervous or muscular tissue by the passage of a 
voltaic current. 

In electro-metallurgy, the process of covering any con- 
ducting surface with a metallic coating by electrolytic de- 
position, such, for example, as the thin copper coating 
deposited on the carbon pencils or electrodes used in systems 
of arc lighting. 

This term is borrowed from the French, in which it has the 
above signification. It is preferably replaced by the term 
electro-plating. (See Electro-Plating.) 

It is never correctly applied to the process for covering iron 
with zinc or other metal by dipping the same in a bath of 
molten metal. 

Galvanized Iron.— Iron covered with a layer of zinc by 
dipping in a bath of molten zinc. 

The process of galvanizing iron is designed to prevent the 
corrosion or rusting of the iron on exposure to the air. (See 
Metals, Electrical Protection of.) 

Galvano-Canterj .— (See Cautery, Electric.) 

Galvano-Faradization.— In electro therapeutics the 
simultaneous excitation of a nerve or muscle by both a voltaic 
and a farad ic current. 

Galvanometer.— An apparatus for measuring the 
strength of an electric current by the deflection of a magnetic 
needle. 

The galvanometer depends for its operation on the fact 
that a conductor, through which an electric current is flowing, 



290 



A DICTIONARY OF ELECTRICAL 




will deflect a magnetic needle placed near it. This deflection 

is due to the magnetic field caused by the current. (See 

Field, Magnetic, of Current.) 

This action of the current 
was first discovered by Oer- 
sted. A wire conveying a 
current in the direction shown 
by the straight arrow, Fig. 
212, or from -f to — , will 
deflect a magnetic needle in 
the direction shown by the 
curved arrows. 
Fi $>- m - If the wire be bent in the 

form of a hollow rectangle F D E G, Fig. 213, and the needle, 

M, be placed inside the circuit, the upper and lower branches of 

the current, will deflect 

the needle in the same 

direction, and the effect 

of the current will thus 

be multiplied. Mercury 

cups are provided at A, 

B and C, for a ready 

change in the direction 

of the circuit. (See 

Astatic Needle.) 
This principle of the 

multiplication of the 

deflecting power of the 

current was applied to 

galvanometers by Ftg - m - 

Schweigger, who used a number of turns of insulated wire for 

the greater deflection of the needle. He called such a device 

a multiplier. In extremely sensitive galvanometers very 

many turns of wire are employed, in some cases amounting 

to many thousands. Such galvanometers are of a high resist- 




WORDS, TERMS AND PHRASES. 



291 



a nee. Others, of low resistance, often consist of a single turn of 
wire and are used in the direct measurement of large currents. 
A Schweigger's multiplier or coil C C, of many turns of 
insulated wire, is shown in Fig. 214. The action of such a 
coil, on the needle M, is comparatively great, even when the 
current is small. 

In the case of any galvanometer, the needle when at rest, 
and no current is passing, should in general, occupy a posi- 
tion parallel to the length of the coil. On the passage of the 
c u r rent t h e 
needle tends to 
place itself in a 
position at right 
angles to the di- 
rection of the cur- 
rent, or to the 
length of the con- 
ducting wire in 
the coil. The 
strength of the 
current passing is Fig. 81U. 

determined hy observing the amount of this deflection as 
measured in degrees on a graduated circle over which the 
needle moves. 

The needle is deflected by the current from a position of 
rest, either in the earth's magnetic field, or in a field obtained 
from a permanent, or an electro magnet. In the first case, 
when in use to measure a current, the plane of the galvano- 
meter coils must coincide with the plane of the magnetic meri- 
dian. In the other case, the instrument may be used in any 
position in which the needle is free to move. 

Galvanometers assume a variety of forms according either 
to the purposes for which they are employed, or to the manner 
in winch their deflections are valued. 

Galvanometer, Absolute A galvanometer 

with an absolute calibration. (See Calibration, Absolute.) 




292 



A DICTIONARY OF ELECTRICAL 



Such a galvanometer is called absolute because if the dimen- 
sions of its coil and needle are known, the current can be de- 
termined directly from the observed deflection of the needle. 

Galvanometer, Aperiodic (See Galvanometer, 

Dead Beat.) 

Galvanometer, Astatic A galvanome- 
ter, the noedle of which is astatic. (See Astatic Needle.) 

Nobili's astatic galvanometer is shown in Fig. 215. The 
astatic needle, suspended by a fibre b, has its lower needle 
placed inside a coil «, consisting of many turns of insulated 

wire, its upper needle moving over 
the graduated dial. The current 
to be measured is led into and from 
the coil at the binding posts x 
and y. 

In this instrument, if small de- 
flections only are employed, the 
deflections are sensibly proportion- 
al to the strength of the deflecting 
^ currents. 

Galvanometer, Ballistic 

A galvanometer 




Fi '9- 215 - designed to measure the strength 

of currents that last but for a moment, such for example, as 
the current caused by the discharge of a condenser. 

The quantity of electricity passing in any circuit is equal 
to the product of the current and the time Since the cur- 
rent caused by the discharge of a condenser lasts but for a 
small time, during which it passes rapidly from zero to a 
maximum and back again to zero, the magnetic needle in a 
ballistic galvanometer takes the form of a ballistic pendulum, 
i. e., it is given such a mass, and acquires such a slow mo- 
tion, that its change of position does not practically begin 
until the impulses have ceased to act. 



"WORDS, TERMS AND PHRASES. 



293 



In the ballistic galvanometer of Siemens and Halske, the 
coils R, R, Fig. 216, have a bell-shaped magnet M, suspended 




Fig. 316. 
inside them by means of an aluminium wire. The magnet is 



294 



A DICTIONARY OF ELECTRICAL 



provided with a mirror S, for measuring the deflections. The 
bell-shaped magnet is shown in elevation at M, and in plan 
at n, s. 

In using the ballistic galvanometer it is necessary to see 
that the needle is absolutely at rest before the discharge is 
sent through the coils. 

Galvanometer, Dead Beat 



A galvanometer, 

the needle of which 
comes quickly to rest, 
instead of swinging re- 
peatedly to and fro. 
(See Damping.) 
Galvano meter, 

Differential 

A galvanometer con- 
taining two coils so 
wound as to tend to de- 
flect the needle in op- 
posite directions. 

The needle of a differ- 
e n t i a 1 galvanometer 
shows no deflection 
when two equal cur- 
rents are sent through 
the coils in opposite 
directions, since, under 
these conditions each 
coil neutralizes the 
other's effects. Such 
instruments may be 
used in comparing re- 
sistances. The Wheatstone Bridge, however, in most cases, 
affords a preferable method for such purposes. (See Balance, 
Wheatstone'' s.) 
A form of differential galvanometer is shown in Fig. 217. 




WORDS, TERMS AND PHRASES. 



295 



Sometimes the current is sent through the two coils so that 
each coil deflects the needle in the same direction. In this 
case, the instrument is no longer differential in action. If 
the magnetic needle, in such cases, is suspended at the exact 
centre of the line which joins the centres of the coils, the 
advantage is gained of obtaining a field of more nearly uni- 
form intensity around the needle. 

Galvanometer, Figure of Merit of 

—(See Figure of Merit of Galvanometer.) 

Galvanometer, Marine A galvanometer 

devised by Sir Wm. Thomson for use on steamships where 
the motion of magnetized masses of iron would seriously dis- 
turb the needles of ordinary instruments. 




Fig. 218. 

The needle of the marine galvanometer is shielded or cut 
off from the extraneous fields so produced, by the use of a 
magnetic screen or shield, consisting of an iron box with thick 
sides, inside of which the instrument is placed. 

The needle is suspended by means of a silk fibre attached 
both above and below, and passing through the centre of 
gravity of the needle. In this manner the oscillations of the 
ship do not affect the needle. 



296 



A DICTIONARY OF ELECTRICAL 



Galvanometer, Mirror A galvanometer in 

which, instead of reading the deflections of the needle directly 
by its movement over a graduated circle, they are read by the 
movements of a spot of light reflected from a mirror attached 
to the needle. 

This spot of light moves over a graduated scale, or its 
movements are observed by means of a telescope. 

A form of mirror galvanometer designed by Sir Wm. 
Thomson, is shown in Fig. 218. The needle is attached 
directly to the back of a light, sil- 
vered glass mirror, and consists of 
several small magnets made of pieces 
of a watch spring. The needle and mir- 
ror are suspended by a single silk fibre 
and are placed inside the coil. A com- 
pensating magnet N S, movable on a 
vertical axis, is used to vary the sen- 
sitiveness of the instrument. The lamp 
L, placed back of a slot in a wide 
screen, throws a pencil of light on the 
mirror Q, from which it is reflected to 
the scale K. 

Galvanometer Shunt.— A shunt 
Fig. 219. placed around a sensitive galvanometer 

for the purpose of protecting it from the effects of a strong 
current, or for altering its sensibility. (See Shunt.) 

The current which will flow through the shunt wire depends 
on the relative resistance of the galvanometer and of the shunt. 
In order that only T V, x£o or nn> o of tne total current shall 
pass through the galvanometer, it is necessary that the re- 
sistances of the shunt shall be the |, -^ or ¥ £ F of the galvanome- 
ter resistance. 

Fig. 219, show r s a shunt, in which the resistances, as com- 
pared with that of the galvanometer are those above referred 
to. The galvanometer terminals are connected at N N. Plug 




WORDS, TERMS AND PHRASES. 



297 



keys are used to connect one or another of the shunts into 
the circuit. (See Multijrfying Poiver of Shunt.) 

Galvanometer, Sine A galvanometer in which 

a vertical coil is movable around a vertical axis, so that it can 
be made to follow the magnetic needle in its deflections. 




Fig. 320. 

In the sine galvanometer the coil is moved so as to follow 
the needle, until it is parallel with the coil. Under these cir- 
cumstances the strength of the deflecting currents in any two 
different cases is proportional to the sine of the angle of de- 
flection. 



298 



A DICTIONARY OF ELECTRICAL 



A form of sine galvanometer is shown in Fig. 220. The 
vertical wire coil is seen at M. A needle, of any length less 
than the diameter of the coil M, moves over the graduated 
circle N. The coil M, is movable over the graduated horizontal 
circle H, by which the amount of the movement necessary to 
bring the needle to zero is measured. The current strength is 
proportional to the sine of the angle measured on this circle, 
through which it is necessary to move the coil M from its 
position when the needle is at rest in the plane of the earth's 
magnetic meridian, until the needle is not further deflected by 
the current, although parallel to the coil M. 

Galvanometer, Tangent An instrument in 

which the deflecting coil consists 
of a coil of wire within which is 
placed a needle very short in pro- 
portion to the diameter of the coil, 
and supported at the centre of the 
coil. 

A galvanometer acts as a tan- 
gent galvanometer only when the 
needle is very small as compared 
with the diameter of the coil. The 
length of the needle should be less 
than one-twelfth the diameter of 
the coil. 

Fig. m. A form of tangent galvanometer 

is shown in Fig. 221. The needle is supported at the exact 
centre of the coil C. 

Under these circumstances the strengths of two different de- 
flecting currents are proportional to the tangents of the angles 
of deflection. Tangent galvanometers are sometimes made 
with coils of wire containing many separate turns. 

Galvanometer, Tangent, — Ohach's.— A form 

of galvanometer in which the deflecting coil, instead of being 
in a fixed vertical position, is movable about a horizontal 




"WORDS, TERMS AND PHRASES. 



299 



axis, so as to decrease the delicacy of the instrument, and thus 
increase its range of work. 

Galvanometer, Torsion A galvanometer in 

which the strength of the deflecting current is measured by 
the torsion exerted on the suspension system. 

A bell-shaped magnet, shown at the right of Fig. 222, is 
suspended by a thread and a spiral spring between two 
coils of high resistance, placed parallel to each other in the 
positions shown. On 
the deflection of the 
magnet, by the cur- 
rent to be measured, 
the strength of the 
current is determined 
by the amount of the 
torsion required to 
bring the m a g n e t 
back to its zero point. 
The angle of torsion 
is measured on the 
horizontal scale at the 
top of the instrument. 

In the torsion gal- 
vanometer, unlike the 
electro-dynamometer, 
the action between the 
coils and the movable 
magnet is as the cur- 
rent strength causing 
the deflection. In the 
electro dynamometer, Fig. 222. 

such an increase in the deflecting coil produces a corresponding- 
increase in the deflected coil ; the mutual action of the two 
is as the square of the current strength causing the deflection. 

Galvanometer, Vertical A galvanometer, the 

needle of which is capable of motion in a vertical plane only. 




300 



A DICTIONARY OF ELECTRICAL 



In the vertical galvanometer the north pole is weighted so 
that the needle assumes a vertical position when no current is 
passing. In the form shown, in Fig. 223, two needles are some- 
times employed, one of which is placed inside the coils C, C. 

The vertical galvanometer is not as sensitive as the ordinary 
forms. It is employed, however, in various forms for an 
electric current indicator or even for a rough current 
measurer. 



Galvanometer, Volt-Meter 



■ — An instrument 
devised by Sir Wm. Thomson, for the measurement of differ- 
ences of electric potential. 

This instrument is so arranged that by a simple correction 

for the varying 
strength of the 
earth's field in any 
place, the results are 
read at once in volts. 
A coil of insulated 
wire, shown at A, 
Fig. 224, has a resist- 
ance of over 5,000 
ohms. A magnetic 
needle, formed of 
short parallel 
needles placed above 
one another and 
called a magnetome- 
ter needle, is attached 
to a long but light 
aluminium index, 
moving over a grad- 
uated scale. A mov- 
Fig- MS- able, semi-circular 

magnet B, called the restoring magnet, is placed over the 
needle, and is used for varying the effect of the earth's field 




WORDS, TERMS AND PHRASES. 301 

at any point. The sensitiveness of the instrument may be 
varied either by the restoring- magnet, or by sliding the mag- 
netometer box nearer to, or further away from the coil. 

The volt-meter galvanometer depends for its operation on the 
fact that when a galvanometer of sufficiently high resistance 
is introduced between any two points in a circuit, the current 
that passes through it, and hence the deflection of its needle, 
is directly proportional to the difference of potential between 
such two points. 

Galvanometers for the commercial measurement of cur- 
rents assume a variety of forms. They are generally so con- 
structed as to read off the amperes, volts, ohms, watts, etc., 
directly. They are called amperemeters or ammeters, volt- 
meters, ohmmeters, wattmeters, etc. For their fuller descrip- 
tion reference should be had to standard electrical works. 



Fig. 22k. 

Galvano-Plastics.— A term formerly employed to ex- 
press electrotyping or electro-metallurgical processes, but now 
generally abandoned. (See Electro- Met all urgy .) 

Galvaiio-Puncture. — In electro therapeutics the treat- 
ment of diseased parts of the body by the introduction therein 
of electrolytic needles. (See Electro-Puncture.) 

Galvanoscopic Frog.— (See Frog, Galvanoscopic.) 

Ga§-Battery.— A battery in which the elements consumed 
are gases as distinguished from solids. 



302 



A DICTIONARY OF ELECTRICAL 



The electrodes of a gas battery generally consist of plates of 
platinum, or other solid substance which possesses the power 
of occluding oxygen and hydrogen, the lower parts of which 
plates dip into dilute sulphuric acid, and the upper parts are 
respectively surrounded by oxygen and hydrogen gas derived 
from the electrolytic decomposition of the dilute acid. 




Fig. 225. 

A gas battery consisting of plates of platinum dipping 
below into acid liquid, and surrounded in the space above the 
liquid by hydrogen and oxygen H, H' and O, O', etc., respect- 
ively, is shown in Fig. 225. 

In charging this battery an electric current is sent through 
it until a certain quantity of the gases has been produced. 
If, then the charging current be discontinued, a current in 
the opposite direction is produced by the battery. The gas 
battery is in reality a variety of storage battery. (See Storage 
of Electricity. Storage Cells.) 

Gas batteries can also be made by feeding continually a gas 
capable of acting on the positive elements. 



Gas Burner, Automatic 

matic.) 



— (See Burner, Auto- 



WORDS, TERMS AND PHRASES. 303 

Gas Jet Photometer. — A photometer for determining 
the intensity of gas light by measuring- the length of the gas 
jet producing the light when burning under certain circum- 
stances. 

Gas Lighting, Electric Various devices 

employed for the simultaneous electric ignition of a number 
of gas jets from a distance. 

Such devices are operated by moans of minute electric 
sparks which are caused to pass through the escaping- gas jets. 

The spark for this purpose is obtained either by means of 
the extra current from a, spark coil, by means of an induc- 
tion coil or by static discharges. (See Extra Current. Sj)ark 
Coil. Induction Coil.) 

Gases, Oeelusion of (See Occlusion of Gases,) 

Gastroseopc. — An electric apparatus for the illumination 
and Inspection of the human stomach. 

The light is obtained by means of a platinum spiral in a 
glass tube surrounded by a layer of water to prevent undue 
heating - . The platinum spiral is placed at the extremities 
of a tube, provided with prisms, and passed into the 
stomach of the patient. A separate tube for the supply of air 
for theextensior of the stomach is also provided. 

Gauge, Electrometer A device employed in 

connection with some of Sir Wm. Thomson's electrometers to 
ascertain whether the needle connected with the layer of acid 
that acts as the inner coating of the Leyden jar used in con- 
nection therewith, is at its normal potential. 

The gauge consists, as shown in Fig. 226, of an attracted 
disc electrometer. The attracted disc is shown above in the 
cover plate at S, and the attracting disc at B, insulated by rod 
A, but electrically connected by the wire C to the sulphuric 
acid in the Leyden jar. 

Gauge, Wire (See Wire Gauge.) 

Gauss. — The unit of intensity of magnetic field. 



304 



A DICTIONARY OF ELECTRICAL 



The term gauss for unit of intensity of magnetic field was 
proposed by S. P. Thompson as being that of a field whose in- 
tensity is equal to 10 8 C. G. S. units. J. A. Fleming pro- 
poses for the value of the gauss such a strength of field as 
would develop an electro-motive force of one volt, in a wire 
one million centimetres in length, moving through such a 
field with unit velocity. 

Fleming's value for the gauss was assumed on account of 
the small value of the gauss proposed by S. P. Thompson. It 
is 100 times greater in value than Thompson's gauss. 

Sir Wm. Thomson proposes for the value of the gauss such 
an intensity of magetic field as is produced by a current of one 
(ampere) weber at the distance of one centimetre. 




Fig. gse. 

Geissler Tubes. — Vacuum tubes of glass, provided with 
platinum electrodes which are passed through and fused into 
the glass, and designed to show the various luminous effects 
of electric discharges through comparatively low vacua. 

Geissler tubes are made of a great variety of shapes, and 
often include tubes, spirals, spheres, etc,, within other 
tubes. These inclosed tubes are made either of ordinary glass, 
or of uranium glass in order to obtain the effects of fluor- 
escence, or some of the inclosed tubes are filled with fluor- 
escent liquids. 



WORDS, TERMS AND PHRASES. 305 

The vacuum in Geissler tubes is by no means what might 
be called a high vacuum. Indeed, if the exhaustion of the 
tube be pushed too far, much of the brilliancy of the luminous 
effects are lost. 

Two of the many forms of Geissler tubes is shown in Fig. 227. 

Generator, Dynamo-Elect ric An appa- 
ratus in which electricity is produced by the mechanical move- 
ment of conductors in a magnetic field so as to cut the lines 
of force. 

A dynamo-electric machine. (See Dynamo-Electric Ma- 
chine. ) 

Generator, Pyro-Hagnctic An appara- 
tus in which electricity is produced by the combined action of 
heat and magnetism. (See Pyro-Magnetic Generator.) 





Fig. 227. 

Generator, Secondary (See Secondary Gene- 
rator.) 

Geographical Equator. (See Equator, Geographical.) 

Geographical Meridian. (See Meridian, Geograph- 
ical.) 

Gilding, Electric The electrolytic deposition 

of gold on any object. 

The object to be gilded is rendered a conductor on its sur- 
face and connected to the negative terminal of a voltaic cell or 
other source, and immersed in a plating bath containing a so- 



306 



A DICTIONARY OF ELECTRICAL 



lutionof a salt of gold, opposite a plate of gold connected with 
the positive terminal of the source. The objects to be plated 
thus becomes the kathode, and the plate of gold the anode of 
the plating bath. On the passage of the current, the gold is 
dissolved from the plate at the anode and deposited on the ob- 
ject at the kathode. (See Kathode. Anode.) 

Gimbals. — Concentric rings of brass, suspended on pivots 
in a compass box, and on which the compass card is supported 
so as to enable it to remain horizontal notwithstanding the 
movements of the ship. (See Azimuth Compass.) 

Each ring is suspended on two 
pivots which are directly opposite 
each other, that is, at the ends of a 
diameter, but this diameter in one 
ring is at right angles to that in the 
other. 




Fig. 228. 



Globular Lig lit iiinj;.— A 

variety of lightning in which the 
electricity appears in the form of 
a ball or globe which floats quietly 
about, and at last explodes with a 
loud detonation. 
Its cause is but little understood. 
The actual existence of these balls or globes is doubted by 
some, who regard them as optical effects produced by the per- 
sistence of the optical impression of a discharge. 

Glow Discharge. (See Discharge, Conveetive.) 
Gold Bath. (See Baths, Gold, etc.) 

Gold-Leaf Electroscope. — An electroscope in which 
two leaves of gold are used to detect the presence of an electric 
charge, or to determine its character whether positive or ne- 
gative. 

When a charge is imparted to the knob C, Fig. 228, the 



WORDS, TERMS AND PHRASES. 307 

gold leaves n, n, diverge. This will occur whether the charge 
be positive or negative. 

To determine the polarity of an unknown charge, the leaves 
are first caused to diverge by means of a known positive or 
negative charge. The unknown charge is then given to the 
leaves. If they diverge still further, then the charge is of the 
same name as that originally possessed by the leaves. If, 
however, they first move together and are then repelled, the 
charge is of the opposite name. 

Governor, Centrifugal (See Centrifugal Gov- 
ernor.) 

Governor, Electric Steam A device used 

in connection with a valve to so electrically regulate the 
supply of steam to an engine, that the engine shall be driven 
at such a speed as will maintain either a constant current or a 
constant potential. 

In the electric governor the steam valve is operated by an 
electro magnet, whose coils, in the case of a constant current 
machine, are of thick wire and are in the main circuit, and in 
that of a constant potential machine are of thin wire and are 
in a shunt around the mains. 

Governors, Electric ■ Devices for electrically 

controlling the speed of a steam engine, the direction of cur- 
rent in a plating bath, the speed of an electric motor, the re- 
sistance of an electric circuit, the flow of water or gas into or 
from a vessel, or for other similar purposes. 

The particular form assumed by the apparatus varies with 
the character of the work it is intended to accomplish. In 
some cases ordinary ball centrifugal governors are employed 
to open or close a circuit ; or, a mass of mercury in a rotating 
vessel is caused at a certain speed to open or close a circuit ; 
or, the resistance of a bundle of carbon discs is caused to vary, 
either by pressure produced by centrifugal force; or by the 
movement of an armature. 



308 A DICTIONARY OF ELECTRICAL 

Gramme.— A weight equal to 15.43235 grains. (See Metric 
System of Weights and Measures.) 

Gramme Atom.— (See Atom, Gramme.) 

Gramme Moleenlc.— (See Molecule, Gramme.) * 

Gramophone— An apparatus for the recording and re- 
production of articulate speech. (See Phonograph.) 

Graphite. — A soft variety of carbon suitable for writing 
on paper or similar surfaces. 

Graphite is the material that is employed for the so-called 
black lead of lead pencils. It is sometimes called plumbago. 
Strictly speaking the term graphite is only applicable to the 
variety of plumbago suitable for use in lead pencils. 

Graphite is used for rendering surfaces to be plated electric- 
ally conducting, and also for the brushes of dynamos and 
motors. 

Graphophone. — An apparatus for the recording and re- 
production of articulate speech. (See Phonograph.) 

Gravitation. — A name applied to the force which causes 
masses of matter to tend to move towards each other. 

This motion is assumed to be that of attraction, that is, the 
bodies are assumed to be drawn together. It is not impos- 
sible, however, that they may be pushed together. 

Gravitation, like electricity, is well known, so far as its 
effects are concerned ; but, as to the true cause of either, par- 
ticularly the former, we are in comparative ignorance. 

The general facts of gravitation may be succinctly stated by 
the following law : 

Every particle of matter in the universe is attracted by 
every other particle of matter, and itself attracts every other 
particle of matter, with a force which is directly proportional 
to the product of the masses of the two quantities of matter 
and inversely proportional to the square of the distance 
between them. 



WORDS, TERMS AND PHRASES. 



309 



-The centre of weight of a 



Gravity, Centre of - 

body. 

Bodies supported at their centres of gravity are in equili- 
brium, since their weight is then evenly distributed around the 
point of support. 

Greiict's Voltaic Cell.— {Cell, Voltaic.) 
Grid. — A lead plate in the form of a gridiron, i. e., pro- 
vided with perforations, _, 

and employed in storage 
cells for the support of 
the active material. (See 
Secondary Cells.) 

Grotliiiss' Hypo- 
thesis. — A hypothesis 
devised by Grothuss to 
account for the electroly- 
tic phenomena that occur 
on closing the circuit of a 
voltaic cell. 

T h i s hypothesis as- 
sumes 

(1) That before the cir- 
cuit is closed, the mole- 
cules of the electrolyte 
are arranged in an ir- 
regular or unpolarized condition, asrepresented in Fig. 229. 
These molecules are shaded, as 
shown in Fig. 230, to indicate their 
composition and polarity. 

(2) When the circuit is closed, and 
a current begins to pass, a polariza- 
tion of the electrolyte, as shown at (2), 
Fig. 230. ensues, whereby all the negative 

ends of the molecules of hydrogen sulphate, or sulphuric 
acid r are turned towards the positive, or the zinc plate, and 




Fig. 229. 




310 A DICTIONARY OF ELECTRICAL 

the positive ends, towards the negative, or the copper plate. 
This, as will be seen, will turn the S0 4 ends toward the zinc, 
and the H 2 ends towards the copper. 

(3) A decomposition of the polarized chain whereby the S0 4 
unites with the zinc, forming Zn S0 4 , and the H 2 liberated 
reunites with the S0 4 of the molecule next to it in the 
chain, and its liberated H 2 with the one next to it, until the 
last liberated H 2 is given off at the surface of the copper or 
negative plate. This leaves the chain of molecules as shown 
at (3). 

(4) A semi-rotation of the molecules of the chain as at (3), 
until they assume the position shown at (4). This rotation 
is required since the molecules in (3) are turned with their 
similar poles towards similarly charged battery plates. 

Ground or Earth-Grounded Wire.— The earth or 
ground which forms part of the return path of an electric cir- 
cuit. 

A circuit is grounded when it is completed in part by the 
ground or earth. 

Grounded Circuit.— (See Circuit, Grounded.) 

Grove's Voltaic Cell.— (See Cell, Voltaic.) 

Giltta-Perclia. — A resinous gum obtained from a tropical 
tree, and valuable electrically for its high insulating powers. 

Gutta-percha readily softens by heat, but on cooling be- 
comes quite hard and tough. Unlike india rubber, it possesses 
but little elasticity. Its specific inductive capacity is 4.2, 
that of air being 1, and of vulcanized india rubber 2.94. (See 
Capacity, Specific Inductive.) 

Gym no tu* Electricus.— The electric eel. (See Eel, Elec- 
tric.) 

Hail, Assumed Electric Origin of — A 



hypothesis, now generally rejected, framed to explain the 
origin of the alternate layers of ice and snow in a hail stone, 



WORDS, TERMS AND PHRASES. 311 

by the alternate electric attractions and repulsions of the 
stones between neighboring-, oppositely charged, snow and 
rain clouds. 

It is now generally recognized that the electric manifesta- 
tions attending hail storms, are the effects and not the causes 
of the hail. (See Paragrelcs.) 

Hair, Electrolytic Removal of The per- 
manent removal of hair by the electrolytic destruction of the 
hair follicles. 

A negative platinum electrode is inserted in the hair follicle 
and the positive electrode, covered with moist sponge or 
cotton, is held in the hand of the patient. A current of two 
to four milliamperes from a battery of from eight to ten 
Leclanche elements is then passed for from ten to thirty sec- 
onds. A few bubbles of gas appear, and the hairs are then 
removed from the follicle by a pair of forceps. (See Milliam- 
p&res.) 

When the work is properly done there is no destruction of 
the skin and therefore no marks or scars. 

In the removal of hair from the face, it is preferable that 
the current should slowly reach its maximum strength. 

Hall EfTeet.— (See Effect, Hall.) 

Hanger-Board of Electric Lamp.— A board furnished 
with a hand switch and hooks for connecting it with a circuit, 
and provided with means for readily placing an arc lamp in 
the circuit. 

The lamp is connected by the mere act of hanging it in 
position, though binding posts are generally connected with 
the board, for the purpose of more thoroughly connecting the 
lamp terminals with the circuit. 

Hanger, Cable or Clip.— (See Cable Clip.) 

Harmonic Receiver. — (See Receiver, Harmonic.) 

Harmonic Telegraphy. — (See Telegraphy, Harmonic.) 

Head Eight, Locomotive Electric An 



312 A DICTIONARY OF ELECTRICAL 

electric light placed in the focus of a parabolic reflector in 
front of a locomotive engine. (See Light House Illumina- 
tion.) 

Heat. — A form of energy. 

The phenomena of heat are due to a vibratory motion im- 
pressed on matter by the action of some form of energy. 

Heat in a body is due to the vibrations or oscillations of its 
molecules. Heat is transmitted through space by means of 
a wave motion in the universal ether. This wave motion is 
the same as that causing light. 

A hot body loses its heat by producing a wave-motion in 
the surrounding ether. This process is called radiation. 

Radiant Energy, or energy transmitted by means of ether 
waves, is of two kinds, viz. : 

(1) Obscure Heat, or heat, which does not affect the eye, 
although it can impress a photographic image on a sufficiently 
sensitive photographic plate. 

(2) Luminous Heat, or heat which accompanies light. 
Heat is conducted, or transmitted through bodies, with 

different degrees of readiness. 

Some bodies are good conductors of heat, others are poor 
conductors. 

Heat is transmitted through the mass of liquids by means of 
currents occasioned by differences in density caused by differ- 
ences of temperature. These currents are called convection 
currents. 

Heat is measured as to its relative degree of intensity by the 
thermometer. It is measured as to its amount or quantity by 
the calorimeter. (See Thermometer. Calorimeter.) 

The heat unit is the calorie, or the amount of heat required 
to raise one gramme of water one degree centigrade. 

Another heat unit, very generally employed in the United 
States and England, is the quantity of heat required to raise 
one pound of water 1° Fahrenheit. (See Calorie, Heat Unit, 
English. Joule. Volt- Coulomb.) 



WORDS, TERMS AND PHRASES. 313 

Heat, Absorption and Generation of in 

Voltaic Cells. — The heat effects which attend the action of 
a voltaic cell. 

The chemical solution of the positive plate or element of a 
voltaic cell, like all cases of chemical combination, is attended 
by a development of heat. 

"When, however, the circuit of the cell is closed, the energy 
liberated during the chemical combination, appears as elec- 
tricity, which develops heat in all parts of the circuit. (See 
Heat, Electric. Cell, Voltaic.) 

Heat, Atomic A constant product obtained by 

multiplying the specific heat of an elementary substance by 
its atomic weight. (See Atomic Weight.) 

The product of the specific heat of all elementary substances 
by their atomic weights is nearly the same. This product is 
called the atomic heat, and is about equal to C.4. 

If, therefore, a number of grammes of any substance, such 
for example as chlorine, be taken numerically equal to its 
atomic weight, viz., 35.5, this number, called the gramme 
atom of chlorine, will represent the number of small calories 
of heat required to raise one gramme-atom of such substance 
through 1° C. (See Calorie.) 

Heat, Electric The heat developed by the pass- 
age of the electric current through any conductor. 

Heat is developed by the passage of the current through 
any conductor, no matter what its resistance may be. 

If the conductor is of considerable length, and of good con- 
ducting power, the heat developed is not very sensible since 
it is spread over a considerable area, and is rapidly lost by 
radiation. (See Heat.) 

H, the heat generated in any conductor of a resistance R, 
by the passage through it of an electric current C, is equal to 
H = C 2 R, in watts. 

But one watt = .24: small calorie per second. 



H =°'(i) 



314 A DICTIONARY OF ELECTRICAL 

Therefore, the heat which is generated, 

H=C 2 Rx .24 calories per second. 

For the case of a uniform wire of circular cross section the 
resistance R, in ohms, is directly proportional to the length 
7, and inversely proportional to, the area of cross section 
7tr 2 , or 

7 

R = ; that is, 

7TV 2 , ' nr 

The temperature to which a wire of a given resistance is 
raised, will of course vary with the mass of the wire, its radia- 
ting surface, and its specific heat capacity. If the same num- 
ber of heat calories are generated in a small weight of a conduc- 
tor, whose radiating surface is small, the resulting temperature 
will of course be far higher than if generated in a larger 
mass provided with a much greater radiating surface. In 
general, however, its temperature increases as the square of 
the current strength, and as the resistance of the wire per 
unit of length is greater. 

The temperature a wire acquires by the passage of a current 
through it varies with the third power of the radius. If two 
wires of the same material have the same lengths, but differ- 
ent radii, the temperature acquired by the passage of an elec- 
tric current wiH. depend on the heat developed per second 
less that radiated per second. Since the former varies as 

1 

— , and the latter as r, that is, as 7 x 27tr, the temperature 
r 2 

1 1 

attained varies as — , and not as — , as frequently stated. 

{Larden.) 

The current required to raise the temperature of a bare 
copper wire a given number of degrees above the tempera- 
ture of the air is given in the following table 



WORDS, TERMS AND PHRASES. 



315 



Bare Copper Wires, 

Current required to increase the temperature of a copper wire t° centigrade 
above the surrounding air, the copper wire being bright polished, or blackened. 



Diameter in 
Centimetres 


CURRENT IN AMPERES. 


(thousanths 
of an inch.) 


t. = 


L°c. 


t. = 9° c. 


t. = 25° c. 


t. = 49° c. 


t. = 81° c. 


Cm. 


Mills. 


Brght 


Black 


Brght Black 


Brght Black Brght Black' Brght Black 


.1 


40 


1.0 


1.4 


3.0 


4.1 


4.8 


6.6 


6.5 


8.9 


7.9 


11.0 


.2 


80 


2.8 


3.9 


8.3 


11.5 


13.5 


18.7 


18.3 


25.3 


22.4 


31.0 


.3 


120 


5.2 


7.2 


15.3 


21.2 


24.9 


34.4 


33.5 


46.4 


41.2 


57.0 


.4 


160 


8.0 


11.0 


23.6 


32.7 


38.3 


53.0 


51.7 


71.5 


63.4 


87.8 


.5 


200 


11.1 


15.4 


33.0 


45.7 


53.5 


74.1 


72.2 


99.9 


88.6 


123 


.6 


240 


14.6 


20.3 


43.4 


60.0 


70.3 


97.4 


94.9 


131 


116 


161 


.; 


280 


18.5 


25.6 


54.6 


75.6 


88.7 


123 


119 


165 


147 


203 


.8 


310 


22.6 


31.2 


66.7 


92.4 


108 


150 


146 


202 


179 


248 


.9 


350 


26.9 


37.3 


79.6 


110 


129 


179 


T74 


241 


214 


296 


1.0 


390 


31.5 


43.6 


93.3 


129 


151 


210 


304 


283 


251 


347 


2.0 


790 


89.2 


123 


264 


365 


428 


593 


577 


799 


709 


981 


3.0 


1180 


164 


227 


485 


671 


787 


1090 


1061 


1468 


1303 


1805 


4.0 


1570 


252 


349 


746 


1035 


1211 


1675 


1633 


2260 


2006 


2776 


5.0 


1970 


353 


488 


1043 


1441 


1692 


2343 


2283 


3160 


2802 


3880 


6.0 


2360 


463 


642 


1371 


1898 


2225 


3080 


3000 


4154 


3685 


5100 


7.0 


2760 


584 


808 


1728 


2392 


2803 


3882 


3781 


5233 


4642 


6426 


8.0 


3150 


714 


988 


2110 


2922 


3422 


4741 


4620 


6396 


5671 


7850 


9.0 


3540 


851 


1178 


2519 


3186 


4088 


5659 


5511 


7630 


6769 


9370 


10.0 


3940 


997 


1380 


2950 


4084 


4788 


6626 


6425 


8935 


7926 


10973 


34.4 






















70000 



(Forbes.) 



316 A DICTIONARY OF ELECTRICAL 

Heat, Molecular The number of calories of heat 

required to raise the temperature of one gramme-molecule of 
any substance 1° C. (See Heat, Atomic.) 

Heat, Specific The capacity of a substance for 

heat as compared with the capacity of an equal quantity of 
water for heat. 

Different amounts or quantities of heat are required to raise 
the temperature of a given weight of different substances 
through one degree. The specific- heats of substances are 
generally compared with water or with hydrogen, the capa- 
city of these substances for heat being very great. 

The specific heat of all elementary atoms is the same. 
For example, the heat energy of an atom of hydrogen is 
equal to that of an atom of oxygen, but since the latter weighs 
sixteen times as much, a given mass of hydrogen contains 
sixteen times as many atoms as an equal mass of oxygen ; 
therefore, when compared weight for weight, hydrogen lias a 
specific heat sixteen times greater than that of oxygen. 

Or, in general, comparing equal iveights, the specific heat 
of an elementary substance is inversely proportional to its 
atomic ivcight. (See Calorimeter.) 

Heat, Specific of Electricity.— (See Specific 

Heat of Electricity.) 
Heat Unit, English, or British Thermal Unit.— 

The quantity of heat required to raise the temj>erature of one 
pound of water 1° F. 

This heat unit represents an amount of work equivalent to 
772 foot-pounds. (See Mechanical Equivalent of Heat.) 
1 Foot Pound = 13,562,600 Ergs. (See Erg.) 

Heat Unit, or Calorie. — The quantity of heat required 
to raise the temperature of one gramme of water 1° C. 

The calorie is sometimes taken as the amount of heat re- 
quired to raise the temperature of 1,000 grammes of water 
1° C. These are termed, respectively, the Small Calorie and 
the Large Calorie. (See Calorie.) 



WORDS, TERMS AND PHRASES. 317 

Heat Unit, or Joule. — The quantity of heat developed 
by the passage of a current of one ampere through a resis- 
tance of one ohm. (See Joule.) 

1 Joule = .24 Calorie. 

1 Foot Pound = 1.356 Joule. 

Heater, Electric A device for the conversion 

of electricity into heat for the purposes of artificial heating-. 

Electric heaters consist essentially of coils or circuits of 
some refractory substance of high resistance, through which 
the current is passed. These coils or circuits are surrounded 
by air or finely divided solids, and placed inside metallic boxes, 
or radiators, which throw oil' or radiate the heat produced. 

When employed for the heating of liquids the coils are 
placed directly in the liquid to be heated, or are surrounded 
by radiating boxes that are placed in the liquid. 

Heating Effects of Currents.— (See Heat, Electric. 
Calorimeter, Electric. Joule's Laws.) 

Hecto (as a prefix.) — One hundred times. 

Helices, Sinistrorsal and Dcxlrorsal Coils 

of wire so wrapped or wound that when traversed b}^ an elec- 
tric current they acquire all the properties of magnets. (See 
Solenoids, Sinistrorsal and Dextrorsal.) 

Heliograph, — An instrument for telegraphic communica- 
tion bj r means of flashes of light, which represent the dots and 
dashes of the Morse alphabet, or the movements of the needle 
of the needle telegraph to the right or left. (See Alphabet 
Telegraphic.) 

The flashes of light are thrown from the surface of a plane 
mirror. Motions to the right or left may be used to distinguish 
between the dots and dashes, or the same purpose may be 
effected by the relative durations of the flashes of light, or by 
the intervals between successive flashes. 

Similar telegraphic communication has been carried on be- 
tween steamers during foggy weather by means of their fog 
horns, or between locomotives, by their steam whistles. 



318 A DICTIONARY OF ELECTRICAL 

Herinel ical Seal.— Such a sealing of a vessel, designed 
to hold a vacuum, or gaseous atmosphere under pressures 
greater or less than that of the atmosphere, as will prevent 
either the entrance of the external atmosphere into the vessel, 
or the escape of the contained gas into the atmosphere. 

Hermetical sealing may he accomplished either by the use 
of suitable cements, or by the direct fusion of the walls of the 
containing vessel. 

Heterostatic.— A term applied by Sir William Thomson 
to an electrometer in which the electrification is measured by 
determining the attraction exerted by the charge to be 
measured and that of an opposite charge imparted to the instru- 
ment by a source independent of the charge to be measured. 

This term distinguishes this electrometer from an idiostatic 
instrument, or one in which the measurement is effected by 
determining the repulsion between the charge to be measured 
and that of a charge of the same sign imparted to the instru- 
ment from an independent source. (See Electrometer.) 

Hicks 9 Automatic Button Repeater.— (See Re- 
peater, Telegraphic). 

Holders for Brushes of Dynamo Electric Ma- 
chines. — A device for holding the collecting brushes of a 
dynamo-electric machine. (See Dynamo-Electric Machines.) 

Holders for Carbons of Arc Lamp.— (See Lamp, 
Electric Arc.) 

Holders for Safety Fuse.— (See Fuse, Safety.) 

Hood for Electric Lamp.— A hood provided for the 
double purpose of protecting the body of an electric lamp 
from rain or sun, and for throwing its light in a general 
d o wnward direction. 

Hoods for arc lamps are generally conical in shape. 

Horizontal Component of Magnetism. (See Com- 
ponent, Horizontal, of Earth's Magnetism.) 



WORDS, TERMS AND PHRASES. 



319 



Horns, Following and 
namo-Electric Machines. - 



Leading, — 

■The ed^es or 



of 



terminals of 



the pole-pieces of a dynamo-electric machine from or towards 
which the armature is carried during its rotation. 

According- to S. P. Thompson, the following horns, b, d, 
Fig. 231, are those towards which the armature is carried ; 
the leading horns, a, c, those from which it is carried. 

As the change in the magnetic intensity is more sudden 
when the armature is moved from the pole pieces, and least 
when moved towards them, it is clear that the leading horns in 
a dynamo-electric machine, and the following horns in an elec- 
tric motor, become 
heated during rotation 
by the production of 
eddy currents. (See 
Currents, Eddy. Dy- 
namo Electric Ma- 
chines. ) 

Horse Power. — 

A commercial unit for / 

rate of doing work. Fig. 231. 

A rate of doing work equal to 33,000 pounds raised one foot 
per minute, or 559 pounds raised one foot per second. 

A careful distinction must be drawn between ivork and 
power. The same amount of work is done in raising one 
pound through ten feet, whether it be done in one minute or 
in one hour. The power expended, or the rate of doing work 
is, however, quite different, being in the former case sixty 
times greater than in the latter. 

Horse-Power, Electric — Such a rate of 

doing electric work as is equal to 33,000 foot-pounds per 
minute, or 550 foot-pounds per second. 

Just as one pound of water raised through a vertical dis- 
tance of one foot requires the expenditure of a foot-pound of 
energy, so one coulomb of electricity acting through the differ- 




320 A DICTIONARY OF ELECTRICAL 

ence of potential of one volt requires a certain amount of work 
to be done on it. (See Coulomb. Volt. Potential.) 

This amount is called a volt-coulomb or joule and, measured 
in foot-pounds, is equal to .737324 foot-pounds. The volt- 
coulomb, or the joule, is therefore the unit of electric work, 
just as the foot-pound is the unit of mechanical ivork. 

The electric work of any circuit is equal to the product of 
the volts by the coulombs. 

If we determine the rate per second at which the coulombs 
2)ass, and multiply this product by the volts, we have a 
quantity which represents the electrical power, or rate of 
doing electrical ivork. But one ampere is equal to one 
coulomb per second; therefore, if we multiply the current in 
amperes by the difference of potential in volts, the product is 
equal to the electrical power or rate of doing- electrical work. 

The product of an ampere by a volt is called a volt-ampere, 
or a watt. 

One Watt = .0013406 Horse-power, or 

One Horse-power = 745.941 Watts. 

Therefore the Electrical Horse-power = , 

1 746 

where C = the current in amperes, and E = the difference of 

potential in volts. 

Hor§eslioe Magnet. — A magnetized bar of steel or 
iron bent in the form of a horseshoe, or letter U. 

A compound horseshoe magnet is shown in Fig-. 232. It 
consists of separately magnetized plates placed with their 
similar poles together. 

A horseshoe magnet possesses greater portative power than 
a straight bar magnet. (See Portative Power.) 

(1) Because its opposite poles are nearer together, and 

(2) Because the magnetic resistance of its circuit is less, the 
lines of magnetic force closing through the armature, and thus 
concentrating the magnetic attraction on the armature. 

Electro-magnets are generally made of the horseshoe shape. 



WORDS, TERMS AND PHRASES. 



321 



Human Body, Electric Resistance of The 

electric resistance offered by the human body. 

Accurate data concerning- the resistance of the human body 
are yet to be obtained. 

When the electrodes of any source are applied to the skin, 
the resistance will necessarily vary with the size and position 
of the contacts, the nature of the con- 
tacts, the condition both of the skin 
and the contacts, whether dry or moist, 
and the pathological or other condition 
of the portion acted on. 

The chief resistance offered by the 
human body to the passage of an elec- 
tric current is the skin. It may be 
regarded as a protective covering so 
far as electric currents are concerned. 

The body is composed, generally 
speaking, of solids and liquids. The 
liquids offer paths of less resistance 
than the solids. The blood and nerves 
are probabty the best conducting media 
in the body. The muscles offer a fair 
conducting path from the quantity of 
saline fluids they contain. 

Since the human body, like that of 
all animals, is itself a source of electric 
currents, it is possible that the pas- ■*%• 2S2 - 

sage through it of a current generated from without, would of 
itself greatly alter its electric resistance. 

"Wolfenden found the resistance in fifty healthy persons, 
measured under exactly similar conditions, to vary from 4,000 
to 5,000 ohms. 

Certain diseased conditions of the body appear to cause a 
marked variation in what may perhaps be regarded as a nor- 
mal electric resistance. Charcot made measurements in which 




322 A DICTIONARY OF ELECTRICAL 

it appears that the resistance fell below the normal in certain 
cardiac affections, and in Graves' Disease, Wolfenden cor- 
roborates this, and in eighteen cases of undoubted Graves' 
Disease the resistance was but 500 to 1,500 ohms. In eight of 
these it was less than 1,000 ohms. In ordinary goitre, unlike 
Graves' Disease {Exophthalmic Goitre), no variation of the 
resistance was found. In a case of malignant thyroid it was 
as high as 8,000 ohms. 

In some cases of hemiplegia, it varied from 1,300 to 4,000 
ohms. In some of epilepsy, from 1,000 to 4,000. In three 
cases of cerebral softening, the resistance was about 3,000 ohms 
and in one case of paraplegia, it was 6,500 ohms, and in one 
case of chorea (adult), 350 ohms. (Wolfenden.) 

Hydro-Electric machine, Armstrong's A 



machine for the development of electricity by the friction of 
condensed steam passing over a water surface. 

Steam generated in a suitable boiler, Fig. 233, which is 
insulated, is allowed to escape through a tortuous nozzle, 
from a series of apertures opposite a pointed comb, attached 
to an insulated conductor. The cooling of the steam during 
its passage through a flat box, termed the cooling box, 
connected with the nozzles, causes a partial condensation, so 
that the box always contains a small quantity of water. 

The friction of the drops of water against the orifice and 
possibly their friction against the water surface itself are the 
cause of the electricity. 

A conductor connected with the pointed comb furnishes 
positive electricity. The boiler furnishes negative electricity. 
The hydro-electric machine is not a very economical source of 
electricity, and is only employed for experimental purposes. 
It was discovered accidentally through a shock given to an 
engineer, who placed his hand in a jet of steam escaping from 
a leaking boiler he was endeavoring to mend. The causes 
were first studied by Mr., now Sir Wm., Armstrong, who, in. 
1840, devised the apparatus just described. 



WORDS, TERMS AND PHRASES. 



323 



Hydrometer or Areometer.— An apparatus for de- 
termining the specific gravity of liquids. (See Areometer.) 




Fig. 233. 



Hydrotasimeter, Electric 



-An elec- 



trically operated apparatus designed to show at a distance the 
exact position of any water level. 
In most forms a float placed in the liquid and connected 



324 A DICTIONARY OF ELECTRICAL 

with an electric circuit, breaks this circuit, and, at intervals, 
sends positive impulses into the line when rising, and negative 
impulses when falling. These are registered by means of an 
index moved by a step-by-step motion, positive currents 
moving it in one direction, and negative currents moving 
it in the opposite direction. 

Hygrometer.— An apparatus for determining the amount 
of moisture in the air. 

Hypothesis.— A provisional assumption of facts or 
causes, the real nature of which is unknown, made for the 
purpose of studying the effects of such causes. 

A theory is a more or less accurate expression of some phys- 
ical truth which has been deduced from independently derived 
laws and principles. 

Our notions concerning the causes of electricity have, in 
reality, only reached the stage of hypotheses ; they cannot 
yet be properly considered as having attained the dignity of 
theories. 

Hypothesis, Double Fluid Electric (See 

Double Fluid Electric Hypothesis.) 

Hypothesis, Single Fluid Electric (See Single 

Fluid Electric Hypothesis. ) 

Hypsometer. — An apparatus for determining the eleva- 
tion of a mountain or other place, by obtaining the exact tem- 
perature at which water boils at such elevation. 

The use of a thermometer to measure the height of a moun- 
tain or other elevation is based on the fact that a given de- 
crease in the temperature of the boiling point of water inva- 
riably attends a given decrease in the atmospheric pressure. 
Therefore, as the observer goes further above the level of the 
sea, the boiling point of water becomes lower, and from this 
decrease, the height of the mountain or other elevation may 
be calculated. 



WORDS, TERMS AND PHRASES. 325 

Idio-Electrics. — A name formerly applied to such bodies 
as amber, resins, glass, etc., which are readily electrified by 
friction and which were then supposed to be electric in them- 
selves. 

This distinction was based on an erroneous conception, and 
the word is now obsolete. 

Idiostatic. — A term employed by Sir Wm. Thomson, to 
designate an electrometer in which the measurement is 
effected by determining" the repulsion between the charge to 
be measured and that of a charge of the same sign imparted 
to the instrument from an independent source. (See Hetero- 
statie.) 

Igniter, Jablochkoff A small strip of carbon, 

or carbonaceous paste of readily ignitable material, placed at 
the free ends of the parallel carbons of a Jablochkoff candle, 
for the establishment of the arc on the passage of the current. 

The igniter is necessary in the Jablochkoff electric candle, 
since the parallel carbons are rigidly kept at a constant 
distance apart by the insulating material placed between 
them, and cannot therefore be moved together as in the case 
of the ordinary lamp. (See Candle, Jablochkoff.) 

Ignition, Electric The ignition of a combus- 
tible material by heat of electric origin. 

The electric ignition of wires is generally accomplished by 
electric incandescence. Ignition may be accomplished by 
the heat of the voltaic arc. (See Heat, Electric. Furnace, 
Electric.) 

The ignition of combustible gases is accomplished by the 
heat of the electric spark. (See Burner, Automatic Electric.) 

Illumination, Artificial The employment 

of artificial sources of light to render objects visible. 

A good artificial illuminant should possess the folio wing- 
properties, viz.: 

(1) It should give a general or uniforn illumination as dis- 
tinguished from sharply marked regions of light and shadow. 



326 A DICTIONARY OF ELECTRICAL 

To this end, a number of small lights well distributed are pre- 
ferable to a few large lights. 

(2) It should give a steady light, uniform in its brilliancy, 
as distinguished from a flickering, unsteady light. Sudden 
changes in the intensity of a light injure the eyes and prevent 
distinct vision. 

(3) It should be economical, or not cost too much to produce. 

(4) It should be safe, or not likely to cause loss of life or 
property. To this intent it should, if possible, be inclosed in 
or surrounded by a lantern or chamber of some incom.bustible 
material, and should preferably be lighted at a distance. 

(5) It should not give off noxious fumes or vapors, when in 
use, nor should it unduly heat the air of the space it illumines. 

(6) It should be reliable, or not apt to be unexpectedly 
extingished when once lighted. 

The claims of the electric incandescent lamp as a cheap 
safe, reliable and steady, artificial illuminant, will be evident 
if these points are examined seriatim, viz. : 

(1) The incandescent light is capable of great sub-division, 
and can therefore produce a uniform illumination. 

(2) It is steady and free from sudden changes in its intensity. 

(3) It compares favorably in point of economy with coal oil 
or gas. 

(4) It is safer than any known illuminant, since it can be 
entirely inclosed and can be lighted from a distance, or at the 
burner, without the use of the dangerous friction match. 

The leads, however, must be carefully insulated and pro- 
tected by safety fuses. (See Fuse, Safety.) 

(5) It gives off no gases, and produces far less heat than a 
gas burner of the same candle power. 

It perplexes many people to understand why the incandes- 
cent electric light should not heat the air of a room as much 
as a gas light, since it is quite as hot as the gas light. It 
must be remembered, however, that a gas burner, when 
lighted, not only permits the same quantity of gas to enter 



WORDS, TERMS AND PHRASES. 327 

the room which would pass if the gas were simply turned on 
and not lighted, but that this bulk of gas is still given off, and 
is even considerably increased, by the combination of the illu- 
minating gas with the oxygen of the atmosphere, and which 
moreover, it is given off as highly heated gases. Such gases 
are entirely absent in the incandescent electric light, and con- 
sequently its power of heating the surrounding air is much 
less than that of gas lights. 

(6) It is quite reliable and will continue to burn as long as 
the current is supplied to it. 

Illumination, Light House Electric— (See 

Light House Illumination, Electric). 

I Hum in at ion, Unit of — — A standard of illumina- 
tion proposed by Preece, equal to the illumination on a sur- 
face such as a street, given by a standard candle at the dis- 
tance of 12.7 inches. 

According to Preece, the illumination for the average streets 
of London, where gas is emploj'ed, is equal to about one-tenth 
this standard, in the neighborhood of a gas lamp, and about 
one-fiftieth, in the middle space between two lamps. 

The term, unit of illumination, in place of the intensity of 
light, was proposed by Preece, in order to avoid the very 
great difficulty in determining the intensity of a light in a 
street or space where there were a number of luminous 
sources, and where the directions of incidence of the different 
lights vary so greatly. 

A carcel standard at the distance of a metre will illumine 
a surface to the same intensity of illumination as a standard 
candle at the distance of 12.7 inches. 

Images, Electrie A term sometimes applied to 

the charge produced in a neighboring surface by induction 
from a known charge. 

A positive charge produces by induction, in a flat metallic 
surface near it, a negative charge which is distributed with 



328 A DICTIONARY OF ELECTRICAL 

varying density over the surface, but acts electrically as would 
an equal quantity of negative electricity placed back of the 
plate, at the same distance the positive charge is in front of it. 
The correspondence of this charge with the image of an 
object seen in a plane mirror has led to the term electrical 
image. 

Maxwell defines electric image as follows: "An electric 
image is an electrified point, or system of points, on one side of a 
surface, which would produce on the other side of that surface 
the same electrical action which the actual electrification of 
that surface really does produce." 

Imponderable. — That which possesses no weight. 

A term formerly applied to the luminiferous or universal 
ether, but now generally abandoned. It is very questionable 
whether it is possible for any form of matter to be actually 
imponderable, or to possess no attraction for other matter 

An imponderable fluid, as for example the universal ether, 
as the term is now generally employed, is a fluid whose 
weight is comparatively small and insignificant, and not a 
fluid, an indefinite quantity of which would be entirely devoid 
of weight. 

Ineaiideseenee, Electric The electric 

heating of a substance, generally a solid, to luminosity. 

Electric incandescence of solid substances differs from 
ordinary incandescence, in the fact that unless the sub- 
stance is electrically homogeneous throughout, the tempera- 
ture is not uniform in all parts, but is highest in those por- 
tions where the resistance is highest and the radiation small- 
est. The deposition of carbon in and on a carbon conductor 
by the flashing process is quite different as performed by 
electrical incandescence, than it would be if the carbons were 
heated by ordinary furnace or other heat. (See Flashing of 
Carbons.) 

Inclination Compass, or Inclinometer.— A mag- 
netic needle so arranged as to readily permit the measurement 



WORDS, TERMS AND PHRASES. 320 

of the magnetic dip at any place. (See Dipping Circle or In- 
clination Compass.) 

Inclination, Magnetic —(See Magnetic Inclina- 
tion.) 

Inclination Map or Chart. — A chart or map on which 
lines are drawn showing - the lines of equal dip or inclination, 
or the isoclinic lines. 

An inclination chart is shown in Fig - 234. 

It will be seen that the magnetic equator, or line of no dip, 
does not correspond with the geographical equator, being 
generally north of the equator in the eastern hemisphere, and 
south of it in the western. The figures attached to the lines 
indicate the value of the angle of dip. 

Inclination or Dip of Magnetic Needle.— The 
deviation of an evenly weighted magnetic needle from a 
horizontal position. 

The direction of a magnetic needle in all parts of the earth, 
except at the magnetic equator, differs from a level or hori- 
zontal position. One of its ends inclines or dips towards the 
ground. (See Dip, Magnetic. Dipping Needle.) 

India Rubber. — A resinous substance obtained from 
the milky juices of several tropical trees. 

India rubber is quite elastic and possesses high powers of 
electric insulation. When vulcanized or combined with 
sulphur, instill retains its powers of electric insulation in a high 
degree. In this state it is readily electrified by friction. (See 
Caoutchouc). 

Indicating Bell. — (See Bell, Indicating.) 

Indicators, Electric Various devices, generally 

operated by the deflection of a magnetic needle, or the ring- 
ing of a bell, or both, for indicating at some distant point the 
condition of an electric circuit, the strength of current that is 
flowing through it, the height of water or other liquid, the 
pressure on a boiler, the temperature, the speed of an engine 



330 



A DICTIONARY OF ELECTRICAL 




WORDS, TERMS AND PHRASES. 331 

or line of shafting, the working of a machine, or other similar 
events or occurrences. 

Indicators are of various forms. They are generally electro- 
magnetic in character. 

Indicators, Electric Circuit Various devices, 

generally in the form of vertical galvanometers, employed to 
indicate the presence and direction of a current in a circuit, 
and often to roughly measure its strength. (See Galvanometer, 
Vertical.) 

Induced Current, Direct Induced Current. — (See 

Current, Extra.) 

Induced Current, Reverse Induced Current. — 

(See Current, Extra.) 

Induction Balance, Hughes' (See Balance, 

Induction, Hughes'.) 

Induction, Dynamo Electric (See Induction, 

Electro-Dynamic.) 

Induction, Electro-Dynamic Electro motive 

forces set up by induction in conductors which are either 
actually or practically moved so as to cut the lines of magnetic 
force. 

These electro-motive forces, when permitted to act or neutral- 
ize themselves, produce a current. 

Electro-dynamic induction occurs only in a magnetic field, 
the intensity of which is either increasing or decreasing. 
It may be produced in the following ways, viz. : 

(1) By the use of an inducing field of varying magnetic in- 
tensity. 

Varying the strength of the current and consequently 
the intensity of its magnetic field, will produce an in- 
duction of the circuit on itself, or a self-induction, and will 
result in extra currents, which are in the opposite direction on 
closing and in the same direction on opening the circuit ; or it 
will produce induction in neighboring conductors which are 



332 



A DICTIONARY OF ELECTRICAL 



within the field of the inducing current. (See Self -Induction, 
Mutual Induction. Currents, Extra.) 

(2) By using an inducing field of practically unvarying 
intensity, and varying the number of lines of magnetic force 
that pass through a conductor, by moving the conductor 
through the inducing field so as to cut its lines of force. 

Or, the conductor remaining fixed in position, the inducing 
field is moved past the conductor by moving the electro-mag- 
net, or electric circuit, or permanent magnet producing the 
field. 

Electro-dynamic induction, therefore, includes . 

(1) Self-induction. 

(2) Mutual Induction, or, as it is sometimes called, Voltaic 
or Current Induction. 

(3) Electro-Magnetic Induction, or Dynamo-Electric Induc- 
tion. 

(4) Magneto-Electric Induction. 




The coil B, Fig. 235, consists of two parallel coils of insu- 
lated wire, the terminals of one of which, called the primary 
coil, are connected with the battery cell P N, and those of the 
other, called the secondary coil, with the galvanometer G. 

Under these circumstances it is found : 

(1) That at the moment of closing the circuit, through the 
primary coil, a momentary current is produced in the second- 
ary coil in a direction opposite to that of the current through 



WORDS, TERMS AND PHRASES. 



333 



the primary, as is shown by the direction of deflection of the 
needle of the galvanometer. 

(2) At the moment of breaking- the circuit through the 
primary coil an induced current is produced in the secondary 
coil in the same direction as that flowing through the primary 
coil. 

(3) These induced currents are momentary, and only con- 
tinue in the secondary while the intensity of the current in 
the primary is varying, i.e., while variations are occurring in 
the strength of the magnetic field in which the secondary coil 
is placed. 

If, for instance, when the current is established in the 
primary coil, and no current exists in the secondary, the 
intensity of the current in the primary be varied by establish- 
ing a shunt circuit across the battery terminals, as by placing a 
short wire d, Fig. 236, in the mercury cups g, g, thus decreas- 
ing the intensity of the current in the primary, an induced 
current will be set up in the secondary circuit in the same 
direction as the primary current. 




Fig. 236. 



From all of these phenomena we see that an increase of cur- 
rent in a conductor produces in a neighboring conductor an 
induced inverse current, or one in the opposite direction to 
the inducing current, while a decrease of such current pro- 



334 



A DICTIONARY OF ELECTRICAL 



duces a direct induced current, or one in the same direction 
as ihe inducing current. 

If the induction coil be made, as in Fig. 237, with its primary 
coil movable into and out of the secondary coil, then the fol- 
lowing' phenomena will occur: 

(1) When the primary coil is moved towards the secondary 
coil an inverse current is induced in the secondary, and, 

(2) When the primary coil is moved away from the second- 
ary coil a direct current is induced in the secondary. 

The movements of permanent magnets towards or from a 
coil will also produce an induced current. 

If, for example, the apparatus be arranged, as in Fig. 238, 
then : 




Fig. 237. 



(1) A motion of the magnet towards the coil produces an 
induced current in the coil in one direction, and 

(2) Its motion away from the magnet produces an induced 
current in the coil in the opposite direction. 



WORDS, TERMS AND PHRASES. 



335 



These induced currents are respectively inverse and direct 
as compared with the direction of the arnperian currents which 
are assumed to produce the magnetic poles of permanent mag- 
nets, or of the currents that actually produce electro magnets. 
(See Magnetism, Ampere's Theory.) 

Induction, Electro-Magnetic (See Induction 

Electro-Dynamic. ) 
These facts may be expressed by the following laws : 
(1) Any decrease in the number of lines of force which pass 
through a circuit produces a direct current in that circuit, 
while any increase in the number of such lines of force which 
pass through any circuit produces an inverse current in that 
circuit. 




Fig. 23S. 

(2) The induced current has an intensity, or more correctly, 
the differences of potential produced are proportional to the 
rate of increase or decrease of lines of force passing through 
the circuit. 

Any conductor therefore, w T hen moved through a magnetic 
field so as to cut the lines of magnetic force, will have a 
current produced in it by induction. 



336 



A DICTIONARY OF ELECTRICAL 



A simple but effective manner of remembering the direction 
of such currents is that proposed by Fleming*. 

If the hand be held with the fingers extended, as in Fig. 239, 
and the direction of the fore finger represent the positive direc- 
tion of the lines of force, i. e., those coming out of the N. pole 
of a magnet, then, if a wire or other conductor be moved in 
the direction in which the thumb points, so as to cut these 
lines of force at right angles, that is if the conductor have its 
length moved directly across these lines, it will have an 
induced current developed in it m the direction in which the 
middle finger points. (See Direction of Lines of Force). 

Or, the same thing* can, 
perhaps, be e v e n more 
eadily remembered by cut- 
ting a piece of paper in the 
shape shown in Fig. 240, 
marking it as shown, and 
then bending the arm P, 
upwards at the dotted line, 
so as to form three axes at 
right angles to one an- 
other. 

As has been already re- 
marked, a differ ence of 
potential is produced by 
the motion of a conductor 
through a magnetic field so 
as to cut its lines of force, 
and not a current. 

It can be shown that in 
order to generate a differ- 
ence of potential of one 
volt, 100,000,000 C. G. S. 
lines of force must be cut per second. 

In electro-magnetic induction the induced current is pro- 
duced by the energy absorbed by moving the conductor through 



JJfrectcons 
of Current. 




WORDS, TERMS AND PHRASES. 



33T 



the field. Lenz has shown that in all cases of electro-magnetic 
induction, produced by the movement either of the circuit or 
of the magnet, the current induced in 
the circuit is in such a direction as to 
produce a magnet pole which would 
tend to oppose the motion. 

For mutual attraction and repulsion 
of currents see Electro-Dynamics. 



X c 



Induction, Electrostatic 



P .2 
3 



-The production of an electric 



o . 

Ml 



Direction of 
Motion. 



M. 



charge in a conductor brought into an 
electrostatic field. 

If the insulated conductor A B, Fig. 
241, be brought into the positive elec- 
trostatic field of the insulated conductor 
C, then, 

(1) A charge will be produced on A 
B, as will be indicated by the divergence of the pith balls. 

(2) This charge is negative at the end A, nearest C, and 
positive at the end C, furthest from B, as can be shown by an 
electroscope. (See Electroscope.) 



Fig. %0. 





Fig. 2kl. 

(3) The charges at A and B, are equal to each other; for, if the 
conductor A B, be removed from the field of C, without touch- 
ing it, the opposite charges completely neutralize each other, 



338 



A DICTIONARY OF ELECTRICAL 



(4) If, however, the conductor A B, be touched at any 
place by a conductor connected with the earth, it will lose its 
positive charge, and will remain negatively charged when 
removed from the field of C. It is in this manner that the 
electrophones is charged. (See Electrophones.) 

(5) The amount of the charges produced in the conductor, 
A B, can never be greater than that in the inducing body C. 

That is to say, the negative 
electricity at A, may be 
sufficient in amount to 
neutralize the positive 
charge on C, if allowed to 
do so. In point of fact the 




Fig. 21 



amount than the inducing 
charge, according to the 
distance between C and A, 



and the nature and condition of the medium which separates 
them. 

The attractions of light bodies by charged surfaces is due to 
the opposite charge produced on those parts of the light bodies 
that are nearest the charged body. , 

The pith ball B, Fig. 242, suspended by a silk thread between 
an insulated positively charged conductor A, and the unin- 
sulated conductor C, will receive by induction a negative 
charge on the side nearest to A, and a positive charge on the 
side nearest to C. It is therefore attracted to A, where, re- 
ceiving a positive charge, it is repelled to C, where it is dis- 
charged and again assumes a vertical position. Induction 
again occurs, and consequent attraction and repulsion. These 
movements follow one another so long as a sufficient charge 
remains in A. 

Induction Coils. — Parallel coils of insulated wire em- 
ployed for the production of currents by electro-magnetic in- 
duction. (See Induction, Electro-Magnetic.) 



WORDS, TERMS AND PHRASES. 



339 



A rapidly interrupted battery current sent through a coil of 
wire called the primary coil, induces intermittent currents in 
a coil of wire called the secondary coil. 




As heretofore made, the primary coil consists of a few 
turns of a thick wire, and the secondary coil of many turns, 
often thousands, of fine wire. Such coils are generally called 
Ruhmkorff Coils, from the name of a celebrated manufacturer 
of them. 

In the form of Ruhmkorff coil, shown in Fig. 243, the pri- 
mary wire is wound on a core formed of soft iron wires, and 
its ends brought out as shown at/, f ' . The fine wire is wrapped 
around an insulated cylinder of vulcanite, or glass, surround- 
ing the primary coil. This wire is very thin, and in some 
coils is over one hundred miles in length. 

The ends of the secondary coil are connected to the insu- 
lated pillars A and B. 

The primary current is rapidly broken by means of a mer- 
cury break, shown at L, and M, 



340 A DICTIONARY OF ELECTRICAL 

The commutator, shown to the right and front of the base, 
is provided for the purpose of cutting off the current through 
the primary, or for changing its direction. "When a battery 
w 1 deli produces a comparatively large current of but a few volts 
electro-motive force, is connected with the primary, and its 
current rapidly interrupted, a torrent of sparks will pass be- 
tween A and B, having an electro-motive force of many thou- 
sands of volts. 

In such cases, excepting losses during conversion, the energy 
in the primary current, or C E, is equal to the energy in the 
secondary current, or C E'. As much therefore as E', the 
electro-motive force of the secondary current exceeds E, the 
electro-motive force of the primary current, the current 
strength C, of the secondary will be less than the current 
strength C, of the primary. (See Converter, or Trans- 
former.) 

Fig. 244, shows diagramatically the arrangement and con- 
nection of the different parts of an induction coil. 

The core I, I' consists of a bundle of soft iron wires, each of 
which is covered with a thin insulating layer of varnish or ox- 
ide. A primary wire P, P, consisting of a few turns of com- 
paratively thick wire is wound around the core, and a greater 
length of thin wire S, S, is wound upon the primary. This is 
called the secondary. So as not to confuse the details of the 
figure it is represented as a few turns. 

The ends of the battery B are connected to the primary 
wire, through the automatic interrupter, in the manner shown. 
It will be seen that the attraction of the core 1 1', for the vi- 
brating armature H, will break contact at the point o, and 
cause a continued interruption of the battery current. 

The condenser C, C, is connected as shown. It acts to di- 
minish the sparking at the contact points on breaking contact, 
and thus, by making the battery current more sudden, to con- 
sequently make its inductive action greater. 



WORDS, TERMS AND PHRASES. 



841 



Induction Coils, Inverted Conver- 
ters. Transformers. — An inverted induction coil is an in- 
duction coil in which the primary coil is made of a long-, thin 
wire, and the secondary coil of a short, thick wire. 




Fig. 2hU. 

By the use of an inverted coil, a current of high electromo- 
tive force and comparatively small current strength, i. c, bui 
of few amperes, is converted or transformed into a current of 
comparatively small electromotive force and large current 
strength. For the advantages of this see System of Dis- 
tribution by Alternating Currents. 

Inverted induction coils are called converters or transfor- 
mers. (Converter or Transformer.) 



Induction, Lateral 



Induction, Magnetic 



(See Lateral Induction.) 

The production of mag- 
netism in a magnetizable substance by bringing it into a mag- 
netic field. 

When a magnetizable body is brought into a magnetic field 
the following phenomena occur, viz.: 



342 A DICTIONARY OF ELECTRICAL 

(1) The lines of magnetic force pass through the body and 
are condensed upon it. (See Field, Magnetic. Paramagnetic.) 

(2) If the body is free to move around an axis, but not bodily 
towards the magnet pole, it will come to rest with its greatest 
extent or length in the direction of the lines of force ; i. e., in 
the direction in which it will offer the least resistance to the 
lines of force that thread through it. 

(3) The body will therefore become a magnet, its south pole 
being situated where the lines of force enter it, and its north 
pole where they pass out from it. 

(4) The intensity of the induced magnetism will depend on 
the number of lines of force that pass through it. 

(5) The direction of the axis of magnetism will depend 
on the directions in which the lines of force thread through the 
body. (See Axis of Magnetism). 

If a bar of iron N, S, 
Fig. 245, be brought near 
the magnetized bar, N, S, 
poles will be produced in N S" n' 

it by induction, as may be Fig. U5. 

shown by throwing iron filings on it. 

Since the nearer the body to be magnetized is brought to 
the magnetizing pole, the greater will be the number of lines 
of force that thread through it, the greater will be the inten- 
sity of its induced magnetism. This will be greatest when 
the two actually touch each other. 

The production of magnetism therefore by contactor touch 
is only a special case of magnetization by induction. 

The attraction of a magnetizable body by a magnet pole, is 
caused by the mutual attraction which exists between the un- 
like pole produced by induction in the parts of the piece of 
iron nearest the attracting magnet pole. This, it will be seen, 
is the same as the attraction caused by an electric charge. 

Induction, Magneto Electric (See Induction, 

Electro Dynamic.) 




WORDS, TERMS AND PHRASES. 343 

Induction, Mutual Induction produced by two 

neighboring' circuits on one another by the mutual interac- 
tion of their magnetic fields. (See Currents, Extra.) 

Induction, Self Induction produced in a 

circuit at the moment of starting or stopping the currents 
therein, by the induction of the current on itself. (See Cur- 
rent, Extra.) 

Induction Top. — A top consisting of an iron disc sup- 
ported on a vertical axis, which, when spun before the poles 
of a steel magnet assumes an inclined position, through the 
influence of the currents induced in the disc. 

The top maintains the inclined position so long only as the 
strength of the induced currents is sufficiently great ; that is 
while speed of rotation is sufficiently great. 

Induction, Tubes of (See Force, Tubes of, or 

Tubes of Induction.) 

Inductive Capacity, Specific (See Capac- 
ity, Specific Inductive.) 

Inductonieter, Differential An appa- 
ratus for measuring by means of a galvanometer the momen- 
tary currents produced by the discharge of a cable. 

Currents produced by the discharge of a cable are of so 
short a duration that they do not produce much effect on a 
galvanometer needle. 

The inductive charge in a cable, or the quantity of elec- 
tricity produced in it by induction, is 

(1) Directly as the electromotive force of the charging bat- 
tery. 

(2) Inversely as the square root of the thickness of the 
coating of gutta-percha or other insulating material between 
the conducting wires and the metallic sheathing, and 

(3) Directly as the square root of the diameter of the copper 
wire of the conductor. In order to cause the cable discharge 
to more thoroughly affect the galvanometer needle, Mr. 



344 A DICTIONARY OF ELECTRICAL 

Latimer Clark employed a differential instrument with a large 
battery, and three reversing- keys, by means of which he gave 
a rapid successsion of charges to the cable. He called the 
instrument a Differential Inductometer. 

Incluctophone. — A device suggested by Mr. Willoughby 
Smith for obtaining electric communication between trains in 
motion and fixed stations by means of the induction currents 
developed in a spiral of wire fixed on the moving engine, in 
its motion past spirals on the line, into which intermittent 
currents are passed. 

The spiral on the engine is placed in the circuit of a tele- 
phone. (See Telegraphy, Inductive.) 

I ml ii< t oriu m. — A name sometimes applied to a jRuhm- 
korff induction coil. (See Induction Coils.) 

Inertia. — The inability of a body to change its condition 
of rest or motion, unless some force acts on it. 

The inertia of matter is expressed in Newton's first law of 
motion, as follows : 

" Every body tends to preserve its state of rest or of uniform 
motion in a straight line, unless in so far as it is acted on by 
an impressed force." 

All matter possesses inertia. 

Inertia, Magnetic or Lag. — The inability of a 

magnet core to instantly lose or acquire magnetism. 

The magnet core tends to continue in the magnetic state in 
which it was last placed. 

To decrease the magnetic inertia the strength of the mag- 
netizing current is increased and the length of the iron core 
decreased. The iron should also be quite soft. (See Coercive 
Force. Lag, Magnetic.) 

Infinity Plug. — A plug, in a box of resistance coils, in 
which the two pieces of brass it connects are not connected by 
any resistance coil and which, therefore, leaves on unplugging, 
an open circuit or an infinite resistance. 



WORDS, TERMS AND PHRASES. 345 

Ink-Writer, Telegraphic, or Recorder. 

(See Balance, Wheat stone's Electric, Box, Form of.) — A de- 
vice employed for recording the dots and dashes of a tele- 
graphic niessag-e in ink on a fillet or strip of paper. 

Insolation, Electric. — (See Sun Stroke, Elective.) 

Installation. — A term embracing the entire electric plant 
and its accessories required to perform any specified work. 

Insulating Cements.— (See Cements, Insulating.) 

Insulating' Materials. — Non-conducting substances 
which surround a conductor, in order that it may either retain 
an electric charge, or permit the passage of an electric current 
through the conductor without sensible leakage. 

Various gases, liquids, or solids may be employed as insu- 
lators. A high vacuum affords the best known insulation. 

Insulating Stool. — A stool provided with insulating 
legs, on which a person, or other body, maybe placed in order 
to receive an electric charge. 

Insulating Tape.— (See Tape, Insulating.) 

Insulating Varnish.— (See Varnish, Insulating,) 

Insulators, Telegraphic or Telephonic. 

Non-conducting supports, by means of which telegraphic, 
telephonic, electric light wires, or other wires are attached 
to the objects by which they are supported. 

The insulators are generally made of glass, earthenware, 
porcelain, or hard rubber, and assume a variety of forms, 
some of which are shown in Figs. 246, 247, and 248. Of what- 
ever material they are made, it is necessary that the surface 
on which the wire rests, or around which it is wrapped, 
should be smooth so as to avoid abrasion either of its insulat- 
ing covering or of the wire itself. 

Two things are to be considered in the selection of an insu- 
lator, viz. : 



346 



A DICTIONARY OF ELECTRICAL 




(1) The insulating power of the material of which it is com- 
posed, so as to reduce the leakage as much 
as possible. (See Electric Leakage). And, 
(2) The tensile strength of the material, 
so that in case of heavy wires no breaks 
may result from the fracture of the insulator. 
Intensity of Current.— A term some- 
times employed to indicate current strength. 
■Fig. 2h6. (See Amp $ re j 

Intensity of Field. — The strength of a field as meas- 
ured by the number of lines of force 
that pass through it per unit of area of 
cross section. (See Field, Electrostatic. 
Field, Magnetic.) 

Intensity of Light. — The brilliancy 
or illuminating power of a light as 
measured by a photometer in standard 
candles. (See Photometer.) 

Intensity of Magnetization, or 

Magnetic Density.— The strength of Fig. 2hi. 

magnetism as measured by the number of lines of magnetic 
force that pass through a unit of area of cross 
section of the magnet, i. e., a section taken at 
right angles to the lines of force. (See Magnetic 
Density.) 

Interlocking Apparatus. — Devices for me- 
chanically operating railroad switches, and sema- 
phore signals for indicating the position of such 
switches, from a distant signal tower, by means 
of a system of interlocking levers, so constructed 
that the signals and the switches are interlocked, 
so as to render it impossible, after a route has 
Fig. 2hs. once been set up and a signal given, to clear a 

signal for a route that would conflict with the one previously 

set up. 





WORDS, TERMS AND PHRASES, 847 

Intermittent Eartli. — (See Earths.) 
Interrupter. — Any device for interrupting or breaking a 
circuit. 

Interrupter, Automatic -(See Automatic Con- 
tact Breaker.) 

Interrupter, Tuning Fork or Reed 

An interrupter in which the makes and breaks are caused to 
follow one another by the vibrations of a tuning fork or reed. 
The tuning fork or reed is maintained in vibration by any 
suitable means. Such interrupters are applied to various 
uses. Synchronous multiplex telegraphy is an example of 
such uses. 

Inverted Induction Coil*. — (See Converters or Trans- 
formers.) 

Ions. — Groups of atoms or radicals which result from the 
electrolytic decomposition of a molecule. 

The ions are respectively electro-positive and electro-ne- 
gative. The electro-positive* ion appears at the plate con- 
nected with the electro negative terminal, or at the kathode, 
and is called the kathion. 

The electro-negative ion appears at the plate connected 
with the electro-positive terminal, or at the anode, and is 
called the anion. (See Electrolysis. Kathion. Anion.) 

Iron-Clad Magnet.— A magnet in which the magnetic 
resistance is lowered by a casing of iron connected with the 
core and provided for the passage of the lines of magnetic 
force. (See Magnet, Tubular.) 

Isobars, or Isobaric Lines. — Lines connecting places 
on the earth's surface which have at any time the same 
barometric pressure. 

A study of the isobaric lines, or isobars, is of great assist- 
ance in making forecasts or predictions of coming changes in 
the weather. 
Isochronism. — Equality of time of vibration. 



348 A DICTIONARY OF ELECTRICAL 

Isochronous Vibrations or Oscillations.— Vibra- 
tions which perform their to and fro motions on either side of 
the position of rest in equal times. 

The vibrations of a pendulum are isochronous, no matter 
what the amplitude of the swing may be, that is, whether the 
pendulum swings through a large arc or a small arc, provided 
this arc be not very great. All vibrations, therefore, that 
produce musical sounds may be regarded as isochronous. 

lsoclinic Charts. — (See Inclination Map or Charts.) 

Isoclinic Lines. — Lines connecting places that have the 
same angle of magnetic dip or inclination. (See Dip, Mag- 
netic.) 

Isodynamic Lines. — Lines connecting places which have 
the same magnetic intensity. 

The magnetic intensity of a place is determined by the 
number of oscillations that a small magnetic needle, moved 
from its position of rest in the magnetic meridian of any 
place, makes in a given time. This method is similar to that 
employed for determining the intensity of gravity at any 
place by observing the number of oscillations that a pen- 
dulum of a given length makes in a given time at that place. 
If, for example, a magnetic needle at one place makes 211 os- 
cillations in ten minutes, and 245 in the same time at another 
place, the relative magnetic intensities at these places are as 
the squares of these numbers or as 44521 : 60025, or as 1 : 1.348. 

Isodynamic Map or Chart — A map of the earth on a 
Mercator's projection on which isodynamic lines are drawn. 

An isodynamic chart is shown in Fig. 249. It will be ob- 
served that the isodynamic lines do not exactly coincide with 
the isoclinic lines, since the line of least magnetic intensity, 
does not correspond with the line of the magnetic equator. 

The point of least magnetic intensity is found at about lat. 
20° S, and long. 35° W. The point of greatest magnetic in- 
tensity, is found at about lat. 52° N. and long. 92° W. 



WORDS, TERMS AND PHRASES. 



349 




350 A DICTIONARY OF ELECTRICAL. 

Another though weaker point of great magnetic intensity 
is found in Siberia. These are distinguished from the true 
magnetic poles by the term Poles of Intensity. 

The Poles of Verticity, as determined by the dipping needle, 
and the poles of intensity as determined by the needle of os- 
cillation, therefore do not coincide in the northern hemisphere. 

Isogonal Ones. — Lines connecting places that have the 
same magnetic variation or declination. (See Declination, 
Magnetic.) 

Isotonic or JOeclination Map or Chart.— A chart 
on which the isogonal lines are marked. 

In the declination or variation chart, shown in Fig. 250, the 
region of western declination is indicated by the shading. 
There is a remarkable oval patch in the northeastern part of 
Asia, in which the declination is west. A similar oval of de- 
creased declination is seen in the southern Pacific. 

The entire earth acts as a huge magnet with an excess of 
south magnetic polarity in the northern hemisphere. 

It is not known whether the earth possesses more than 
a single pair of magnetic poles, or what is the exact cause 
of its magnetism. The variations in the declination, and 
in the intensity of its magnetism, due to the position of 
the sun, as well as the marked magnetic disturbances that 
accompany the occurrence of sun spots, would appear to con- 
nect the earth's magnetism with the solar radiation. 

It is believed by some that the earth possesses in reality 
the two magnetic poles, viz., a south pole in the northern 
hemisphere, and a north pole in the southern hemisphere. 
(See False Poles, Magnetic.) 

Isotropic Conductor. — A conductor which possesses the 
same powers of electric conduction in all directions. 

An electrically homogeneous medium. 

Isotropic Medium. — A transparent medium which pos- 
sesses the same optical or electric properties in all directions. 

An optically homogeneous, transparent medium. 



WORDS, TERMS AND PHRASES. 



351 




352 



A DICTIONARY OF ELECTRICAL 




An electrically isotropic medium possesses the same powers 

of electric conduction or spe- 
cific inductive capacity in all 
directions. (See Anistropic 
Medium.) 

I, W. Cr. — A contraction 
for Indian Wire Gauge. 

Jar, L.eyden A 

condenser in the form of a jar, 
in which the metallic coatings 
are placed opposite to each 
other on the outside and the 
inside of the jar. 

The metal coatings should 
not extend to more than two- 
Fi 9- 251 - thirds the height of the jar, 

the rest of the glass being varnished to avoid the creeping of 
the charge over the glass in damp weather. 
The inside coating is connected by means 
of a metallic chain, to a rounded knob on 
the top of the jar, as shown in Fig. 251. 
The conductor supporting the knob passes 
through a dry cork or plug of some insulat- 
ing material. 

To charge the jar the outside coating is 
connected with the earth, as by holding it 
in the hand, and the inside coating is con- 
nected with the conductor of a machine. 

Jar, Unit A small Leyden jar 

sometimes employed to measure approxi- 
mately the quantity of electricity passed 
into a Leyden battery or condenser. 

As shown in Fig. 252, the unit jar consists of a small Leyden 
jar/, whose outer coating is connected with a sliding metallic 




WORDS, TERMS AND PHRASES. 353 

rod o, provided at each end with a rounded knob, and the inner 
coating- of which is connected with a metallic knob c, placed, 
and as shown, inside a glass jar d, opposite the ball on the 
long end of b. 

When now the inside of the unit jar, or the end connected 
with c, is connected with the charging source, such as a 
machine, and the outside at a is connected with the battery 
that is to be charged, for every spark that passess between 
d and c, a definite quantity has passed at a. 

The value of this unit charge, may be varied by varying the 
distance between d and c. 

The smaller the unit jar in proportion to the jar to be 
charged, and the shorter the distance between c and d, the 
more reliable are the comparative results obtained. 

Jet Photometer. — An apparatus for determining the 
candle power of a luminous source. (See Carcel, Standard.) 

Jewelry, Electric The substitution of minute 

incandescent electric lamps for the rarer gems in articles of 
jewelry. 

The lamps are lighted by means of small, primary storage 
batteries, carried in the pocket. 

Joint Re§i§tance of Parallel Circuits— The joint 
resistance of two parallel circuits is determined by means of 
the following formula : 

R 



r -\-r' 

Where R = the joint resistance of any two circuits whose 
separate resistances are respectively r and r'. 

When there are three resistances r, r' and r", in parallel, 
the joint resistance, 

-. r r V 

K = 



r r' -J- r r" -\- r' r" 
(See Circuits, Varieties of.) 



354 A DICTIONARY OF ELECTRICAL 

Joint Testing. — Ascertaining the resistance of the in- 
sulating material around the joint in a cable. 

The resistance of a cable at its joint is necessarily high, 
since the joint forms but a small part of length of the cable. 
It should not, however, be large as compared with an equal 
length of another part of the cable with a perfect core. 

Two methods for the testing of cable joints are generally 
employed, viz.: 

(1) A condenser is charged through the joint for a given 
time, and the deflection obtained by its discharge is compared 
with the discharge of the same condenser charged for an 
equal length of time through a few feet of perfect cable. 

(2) A charged condenser is permitted to discharge itself 
through the joint, and the amount lost after a given time 
noted. 

For description of methods, see Kempe's "Handbook of 
Electrical Testing." 

Joints, Butt End to end joints. 

Butt joints are formed by bringing the ends to be joined 
together and securing them while in such position. 

Joints, Butt and Lap for Wires.— Joints 

effected in wires either by placing the wires end on, or by 
overlapping the ends, and subsequently soldering. 

Joints, Butt and Lap of Belts.— The joints in a 

leather belt, employed for transmitting power from a line of 
shafting, where the ends are simply brought together and 
laced, is called a, butt joint, in contradistinction to a lap joint, 
or a joint formed by placing one end of the belt over the other 
and lacing or riveting the two. 

In delicate galvanometers the slightest change in the speed 
of the engine driving the dyna mo-electric machine producing 
the current, causes an annoying fluctuation of the needle that 
prevents accurate reading, when lap joints are used in the 
belt instead of butt joints, unless the former are very carefully 
made. It also causes a flickering in the lights, 



WORDS, TERMS AND PHRASES. 355 

Joint §, Expansion Joints for underground con- 
ductors, tubes or pipes, exposed to considerable changes of 
temperature, in which a sliding joint is provided to safely 
permit a change of length on expansion or contraction. 

Joints, Lap Joints effected by overlapping short 

portions near the ends of the two things to be joined, and secur- 
ing them while in such position. 

Joints, Telegraphic, Telephonic, etc. 

Methods adopted for joining the ends of electric conductors so 
as to insure a permanent junction whose resistance shall not 
be appreciably greater per unit of length than that of the rest 
of the wire. 

In making a joint care should always be taken to clean and 
scrape the insulating material from the wires before twisting 
them together. 

Telegraph wires were formerly joined by the ordinary bell- 
hanger's joint ; that is, the wires were simply looped together. 
The constant vibrations to which the wires are subject caused 
such a joint to be abandoned and an improvement introduced 
by bolting the ends together, as shown in Fig. 253. 

This latter method is now replaced by the following, viz. : 

In the Britannia Joint, shown in Fig. 254, the wires to be 
joined are placed side by side for about two inches, bound 
with No. 16 (British gauge) binding wire, in the manner 
shown, and then carefully soldered. 

The American Twist Joint, shown in Fig. 255, is made by 
twisting the wires together in the manner shown and sub- 
sequently soldering. 

This joint is easily made and is quite serviceable. 

All joints should be soldered, but in so doing care must be 
taken that the soldering liquid or solid employed is free from 
acids or other corrosive materials, and that ail traces of such 
materials are removed before the joint is covered with insulat- 
ing material. 



356 



A DICTIONARY OF ELECTRICAL 



Kerite, Okonite, or other insulating- Tape, should preferably 
be wrapped around the joint after it is soldered. 

In making a joint in a gutta-percha covered wire, such as 
a submarine cable wire, or wires, the following method 
may be employed : The bared and cleansed 



wires are 



^^Bi^feBKStt 



Fig. 253. 

twisted together and soldered. The soldered joint is then 
covered with a layer of plastic insulating material made of a 
mixture of gutta-percha, tar and rosin. (See Chatterton's 
Compound.) In order to insure a good junction between this 
and the gutta-percha covering on the rest of the wire, the 




Fig. 25k. 

outer surface of the gutta-percha is removed for about two 
inches from each side of the joint so as to remove its 
oxidized surface. After the coating is put on, it is warmed 
gently by a warm joining tool and not by the flame of a lamp. 
A sheet of warmed gutta-percha is then wrapped around the 



Fig. 255. 

joint, and while it and the joint are still hot, another coating 
of the plastic, insulating material is applied. Successive 
layers of gutta-percha and insulating material are generally 
applied in the case of submarine cables. (Culley.) 

JouSad. — A term proposed for the Joule, but not gener- 
ally adopted. (See Joule.) 



tfrORDS, TERMS AND PARASES. 357 

Joule. — The unit of electric energy or work. 
The volt-coulomb. 

The amount of electric work required to raise the potential 
of one coulomb of electricity one volt 

The joule may be regarded as a unit of work or energy in 
general, apart from electrical work or energy. 

1 joule = 10,000,000 ergs. 

1 joule. = .73732 foot pound. 

1 joule =1 volt-coulomb. 

4.2 joules = 1 small calorie. 

1 joule per second = 1 watt. 

The British Association recently proposed to call one joule 
the work done by one watt per second. 

Joule Effect. — The heating effect produced by the 
passage of an electric current through a conductor, arising 
merely from the resistance of the conductor. (See Effect, 
Joule.) 

Kaolin. — A variety of white clay sometimes employed for 
insulating purposes. 

Jablochkoff employed kaolin between the parallel carbons 
of his electric candle for the purpose of insulating them. He 
also devised an electric lamp in which a spark of considerable 
difference of potential, obtained from an ordinary induction 
coil, was caused to raise a surface of kaolin to incandescence 
by its passage over it. 

Katheleetrotonus, or Katelectrotonus.— In elec- 
tro therapeutics the condition of increased functional activity 
that occurs in a nerve in the neighborhood of the negative 
electrode, or the kathode applied in medical electricity. (See 
Electrotonus.) 

Kathion. — The electro positive ion, atom, or radical into 
which the molecule of an electrolyte is decomposed by electro- 
lysis. (See Electrolysis. Ions.) 

Kathion is sometimes improperly written cation. 



358 



A DICTIONARY OP ELECTRICAL 



Kathode. — The conductor or plate of a decomposition cell 
connected with the negative terminal or electrode of a battery 
or other source. 

The word kathode is sometimes applied to the negative 
terminal of a battery or source, whether connected with a 
decomposition cell or not. It is preferable, however, to 
restrict its use to a decomposition cell. (See Anode.) 

The word kathode is often improperly written cathode. 



■ PER! POLAR (KA1 


"ELECTRCf 


ro 


iM 


OZONE •--- 


: __polar(ane 


uECTROTQ 
1 1 


N 


c 


ZONE _ : 


j ! ACTUAL 


A\ f 


*N 





DE j \ 




Fig. 256. 

Kathodic and Anodic Electro-Diagnostic Re- 
actions. — The reactions which occur at the kathode or anode 
of an electric source placed on or over any part of a living 
body. 

Fig. 256, from DeWatteville's Medical Electricity, represents 
what he assumes takes place at the points of entrance and 
exit of the current in a nerve submitted to the action of the 
anode of an electric source. Two zones are formed, an anodic 
and kathodic; the virtual anode is formed by the portion of the 
skin nearer the nerve, and the virtual kathode in the adjoin- 
ing muscles. There are thus formed two zones of influence, 



WORDS, TERMS AND PHRASES. 359 

one, immediately around the anode, called the polar, or anelec- 
trotonic zone, and one, surrounding this and including- the 
virtual kathode, and called the peripolar, or katelectrotonic 
zone. 

K. C C — In electro therapeutics, a brief method of writing 
kathodic closure contraction, or the effects of muscular con- 
traction observed by the closure of a circuit at the kathode. 

K. I>. C — In electro therapeutics, a brief method of writing 
kathodic duration contraction, or the effects of muscular con- 
traction observed at the kathode after the current has been 
passing for some time. 

Keeper of Magnet. — A mass of soft iron applied to the 
poles of a magnet through which its lines of magnetic force 
pass. (See Field, Magnetic.) 

The keeper of a magnet differs from its armature in that 
the keeper while acting as such is always kept on the poles to 
prevent loss of magnetization while the armature, besides act- 
ing as a keeper, may be attracted towards, or repelled from, 
the magnet poles. While performing its functions the keeper 
is always fixed; the armature generally, though not always, is 
in motion. 

Opinion is divided, however, on the efficacy of the keeper. 

Key-Board.— (See Board, Switch.) 

Key, Discharge. — A key employed to enable the dis- 
charge from a condenser to be readily passed through a 
galvanometer for purposes of measurement. 

Key, Discharge, Kempe's A discharge key 

constructed as shown in Fig. 257. 

The solid lever, hinged at one extremity, plays between two 
contacts connected to two terminals, and has two finger triggers 
at its free end marked "Discharge" and "Insulate," con- 
nected to two ebonite hooks respectively. The hook at- 
tached to that marked "Discharge" is a little higher than 
the other, so that when the lever is caught against it, the 



360 



A DICTIONARY OF ELECTRICAL 



key rests in an intermediate position between the two con- 
tacts, and when caught against the lower trigger, it rests 
against the bottom contact. When in the last position, a de- 
pression of the ''Insulate" trigger causes the lever to spring 
up against the second hook, thus insulating it from either con- 
tact, and on the depression of the "Discharge" trigger, the 
lever springs up against the top contact. 




Fig. 257. 
Key, Discharge, Webb's — 



A discharge key con- 
structed as shown in Fig. 258. 

A horizontal lever L, Fig. 258, passing between two contacts 
and hinged at J, is pressed upwards by a spring. The free end 
of this lever terminates in two steps 1 and 2. A vertical lever 
H, provided with an insulating handle, is jointed at J', and has, 
at C a projecting metallic tongue that engages in the upper 
step when the lever H, is vertical, and on the lower step when 
it is slightly moved from the free end. 

When the projection C rests on the lower step 2, the lever 
L is intermediate between the top and bottom contacts, and is 
therefore disconnected from either of them ; but, when it rests 
on the upper step, it is in contact with the lower contact. 
When the lever H is so moved as to have the projection C, 
away from both contacts, the lever L is pressed by its spring 
against the upper contact. 



WORDS, TERMS AND PHRASES. 



361 



The battery terminals are connected with the condenser 
terminals when the lever L, is touching the lower contact, but 
when the lever L, touches the top contact, the condenser is 
connected with the galvanometer terminals. 




Fig. 258. 

Key, Double-Contact Form of Bridge Key, 

Sprague's A key designed to close two separate 

circuits successively. 

On depressing K, 
Fig. 259, the contacts 
c, c, are first closed 
and then those ate', c'. 
Metallic pieces 1, 2, 3 
and 4, serve to make 
contacts with appar- 
atus used in connec- 
tion therewith. 

The battery circuit 
is connected to 1 and 
2, and the galvanome- 
ter to 3 and 4, so that the battery circuit is closed first, and 
the galvanometer afterwards. Used in connection with the 
Wlu>atstone Bridffe. 




Fig. 



362 



A Dictionary of electrical 



Key, Double-Contact 



-, Lambert's.— A key used 



in cable work, and constructed as shown in Fig. 260. 
F. .ft* 




In Thomson's method for the determination of electrostatic 
capacity, the capacity of the cable is compared with that of a 
condenser containing- a known charge. These two charges are 
so connected electrically as to discharge into and neutralize 

each other if equal, but if 
not, to produce a gal- 
vanometer deflection by 
a charge equal to their 
difference. 

The connections are 
such that the pushing 
~ forward of K, depresses 
Fig.S6l. k e y S that permit a bat- 

tery to simultaneously charge the condenser and the cable. 
On drawing K, back, the difference of the two charges are 
allowed to mix. Then, on depressing k, the difference of the 
charge, if any, is discharged through the galvanometer. 

Key, Magneto-Electric A telegraph key for 

sending an electric impulse into a line, so arranged that the 




WORDS, TERMS AND PHRASES. 



coil of wire on an armature connected with the key lever, 
is, by the movements of the key, moved towards or from 
the poles of a permanent magnet, the movements of the key 
thus producing the currents sent into the line. 

Key, Plug A simple form of key in which a con- 
nection is readily made or broken by the insertion of a plug 
of metal between two metallic plates that are thus introduced 
into a circuit. 

A form of plug-key is shown in Fig. 261. 

Key, Reversing - -A key, inserted in the circuit 

of a galvanometer for obtain- 
ing deflections of the needle 
on either side of the galvano- 
meter scale. 

The galvanometer termin- 
als are connected to the bind- 
ing posts 2 and 3, Fig. 262, 
and the circuit terminals to 
the other two posts. On de- 
pressing K, the current flows 
in one direction and on de- 
pressing K', in the opposite direction. Clamps, operated by 
handles, are provided so as to close either of the keys per- 
manently, if so desired. 

Key, Sliort-Circuit A key, which in its normal 

condition short-circuits the galvanometer. 

Such a short-circuit key is provided for the purpose of pro- 
tecting the gavanometer from injury by large currents being 
accidentally passed through its coils. In the form shown in 
Fig. 263, the spring S, rests against a platinum contact, but 
when depressed by the insulated head at K, it rests against 
an ebonite contact, and throws the galvanometer into the de- 
sired circuit. 

The key is provided with double binding posts at P and N, 




Fig. 262. 



864 



A DICTIONARY OF ELECTRICAL 



for convenience of attachment to resistance coils, batter- 
ies, etc. 

In the form of short-circuit key shown in Fig. 264 a catch is 
provided for the purpose of keeping the key down when once 
depressed. Its arrangement will be understood from an 
inspection of the figure. 




Fig. 263. 



Key, Sliding-Contaet - 

slide form of Wheatstone's 



The key employed in the 

bridge, to make contact with 

the wire over which the sliding contact passes. (See Balance, 

Wheatstone's, Slide Form of .) 




Key, Telegraphic 



Fig. 26h- 

The key employed for send- 



ing over the line the successive makes and breaks that pro- 
duce the dots and dashes of the Morse alphabet, or the 
deflections of the needle of the needle telegraph. (See Tele- 
graphy, American or Morse System of.) 



WORDS, TERMS AND PHRASES. 365 

Kilo (as a prefix). — One thousand times. 

Kilodyne. — One thousand dynes. (See Dyne.) 

Kilogramme. — One thousand grammes, or 2.2046 lbs. av- 
oirdupois. (See Weights, French System of.) 

Kilojoule. — One thousand joules. 

Kilometre. — One thousand metres. 

Kilowatt. — One thousand watts. 

Kine. — A unit of velocity proposed by the British Asso- 
ciation. 

A kine equals one centimetre per second. 

Kinetie Energy. — Energy which is actually doing work, 
as distinguished from energy that only possesses the power 
of doing work, or potential energy. (See Energy.) 

Kite, Franklin's A kite raised in Philadelphia, 

Pa., in June, 1752, by means of which Franklin experiment- 
ally demonstrated the identity between lightning and elec- 
tricity, and which, therefore, led to the invention of the light- 
ning rod. 

It is true that Dalibard, on the 10th of May, 1752, prior to 
Franklin's experiment, succeeded in drawing sparks from a 
tall iron pole he had erected in France. This experiment was, 
however, tried at the suggestion of Franklin, and must prop- 
erly be ascribed to him. 

The following description of this kite is given by Franklin 
in the following letter : 

Letter XI., from Benj. Franklin, Esq., of Philadelphia, to 
Peter Collinson, Esq., F.R.S., London. 

" Oct. 19, 1752. 

"As frequent mention is made in public papers, from Europe, 
of the success of the Philadelphia experiment for drawing the 
electric fire from clouds by means of pointed rods of iron 
erected on high buildings, etc., it may be agreeable to the 



dbb A DICTIONARY OF ELECTRICAL 

curious to oe informed that the same experiment has succeeded 
in Philadelphia, though made in a different and more easy- 
manner, which is as follows : 

" Make a small cross, of two light strips of cedar, the arms 
so long, as to reach to the four corners of a large thin hand- 
kerchief, when extended ; tie the corners of the handkerchief 
to the extremities of the cross, so you have the body of a kite ; 
which, being properly accommodated with a tail, loop, and 
string, will rise in the air, like those made of paper ; but this, 
being of silk, is fitter to bear the wet and wind of a thunder 
gust without tearing. To the top of the upright stick of the 
cross is to be fixed a very sharp pointed wire, rising a foot or 
more above the wood. To the end of the twine, next the 
hand, is to be tied a silk ribbon, and where the silk and twine 
join, a key may be fastened. This kite is to be raised when a 
thunder gust appears to be coming on, and the person who 
holds the string must stand within a door or window, or under 
some cover, so that the silk ribbon may not be wet ; and care 
must be taken that the twine does not touch the frame of the 
door or window. As soon as any of the thunder clouds come 
over the kite, the pointed wire will draw the electric fire from 
them, and the kite, with all the twine will be electrified, and 
the loose filaments of the twine will stand out every way, 
and be attracted by an approaching finger. And when the 
rain has wet the kite and twine, so that it can conduct the 
electric fire freely, you will find it stream out plentifully from 
the key on the approach of your knuckle. At this key the 
phial may be charged ; and from electric fire, thus obtained, 
spirits may be kindled, and all the other electric experiments 
be performed, which are usually done by the help of a rub- 
bed glass globe or tube, and thereby the sameness of the 
electric matter with that of lightning completely demon- 
strated. B. Franklin." 

Kyanizing". — A process employed for the preservation of 
wooden telegraph poles by injecting a solution of corrosive 



WORDS, TERMS AND PHRASES. 367 

sublimate into the pores of the wood. (See Poles, Tele- 
graphic.) 

Lag:, Magnetic The tendency of the iron core of 

a magnet, or of the armature of a dynamo-electric machine, to 
resist and therefore retard magnetization. 

This retardation, or lag, is called the magnetic lag. 

The lead necessary to give the brushes of a dynamo-electric 
machine to ensure quiet action has by some been erroneously 
ascribed to the magnetic lag. The lead, though due to lag in 
part, is, in reality, mainly due to the resultant magnetization 
of the armature by both the field magnets and by its own cur- 
rent. (See Angle of Lead.) 

This displacement is measured by an angle sometimes called 
the angle of lag. (See Angle of Lag.) 

Lamination of Core. — The subdivision of the core of 
the armature of a dynamo-electric machine into separate in- 
sulated plates or strips for the purpose of avoiding eddy cur- 
rents. 

This lamination must always be perpendicular to the direc- 
tion of the eddy currents that would otherwise be produced. 
(See Eddy Currents). 

Lamellar Di§tribntion of Magneti§ni, Magnetic 
Shell. — The distribution of magnetism in magnetic shells. 

A magnetic shell is a thin sheet or disc of magnetized mate- 
rial whose opposite extended faces are of opposite magnetic 
polarities, and the extent of whose surface is very great as 
compared with its thickness. 

The field produced by a magnetic shell is exactly similar to 
that produced by a closed voltaic circuit, the edges of the 
space inclosed by which correspond to the edges of the mag- 
netic shell. 

Magnetic Density or Intensity, or the number of lines of 
force per unit area of cross section, is equal over all parts of 
the surface of a simple magnetic shell. The strength of such 



368 



A DICTIONARY OF ELECTRICAL 



a shell will therefore be equal to its thickness multiplied by- 
its surface density. 

A magnetic shell may be conceived as consisting of a very- 
great number of exceedingly short, straight, magnetic needles 
placed side by side, with their north poles terminating at one 
of the faces of the sheet and their south 
poles at the opposite face, the breadth of 
the sheet being very great as compared 
with its thickness. Such a distribution of 
magnetism is known as a lamellar dis- 
tribution. 

Lamp, Arc, Electric 




An 

electric lamp in which the light is pro- 
duced by a voltaic arc formed between two 
or more carbon electrodes. 

The carbon electrodes are placed in 
various positions, either parallel, horizon- 
tal, inclined, or vertically one above the 
other. The latter is the form most gen- 
erally adopted, since it permits the ready 
feeding of the upper carbon. 

The carbons are maintained during their 
consumption, at a constant distance apart, 
by the aid of various feeding devices. 
Such devices consist generally of trains of 
wheelwork, mechanical or electric motors, 
or are operated by the simple action of a 
spring, gravity or a solenoid. 

The carbon pencils or electrodes are held 
in carbon holders, consisting of clutches 
or clamps, attached to the ends of the lamp rods. 

When the lamp is not in operation the carbons are usually in 
contact with one another ; but, on the passage of the current, 
they are separated the required distance by the action of an 
electromagnet whose coils are traversed by the direct current. 



Fig. 265. 



WORDS, TERMS AND PHRASES. 369 

In order to maintain the electrodes a constant distance 
apart, the upper carbon is held in position by the operation of 
a clutch in some lamps, or, in others, by a detent, that en- 
gages in a toothed wheel. The position of this clutch or detent 
is controlled by the action of an electro-magnet whose coils are 
usually situated in a shunt or derived circuit, of high resis- 
tance, around the electrodes. When the carbons are at their 
normal distance apart, the shunt current is not of sufficient 
strength to move the clutch or detent from the position in 
which it prevents the downward motion of the upper carbon 
rod. When, however, by the burning or consumption of the 
carbons, the resistance of the arc has increased to an extent 
which can be predetermined, the increased current that is 
thereby passed through the shunt circuit is now sufficiently 
strong to release the clutch or detent, thus permitting the 
fall or feed of the upper carbon. In a well designed lamp this 
occurs so gradually as to produce no perceptible effect on the 
steadiness of the light. 

Arc lamps are generally placed in series circuits, that 
is, the current passes successively through all the lamps 
in the circuit, and returns to the source. In order to avoid 
the breaking of the entire circuit, an automatic safety 
device is provided. This consists essentially of an electro- 
magnet placed in a shunt circuit, so that, when the resist- 
ance of the arc becomes very great, the increased current, 
flowing through the coils of the electro-magnet, produces a 
movement of its armature which closes a short circuit around 
the lamp, and thus cuts it out of the circuit. (See Device, 
Safety.) 

Arc lamps assume a great variety of forms. A well known 
form is shown in Fig. 265. 

Lamp Bracket, Electric (See Bracket, Lamp.) 

Lamp, Carcel (See Car eel Lamp.) 

Lamp, Differential Arc An arc lamp in which 

the movements of the carbons are controlled by the different 



370 A DICTIONARY OF ELECTRICAL 

tial action of two magnets opposed to each other, one of 
whose coils is in the direct, and the other in a shunt circuit 
around the carbons. 

Sometimes the differential coils are placed on the same 
magnet core. 

Lamp-Hours.— The number of lamp-hours is obtained 
by multiplying the number of lamps by the average number 
of hours during which they are burning. 

A method of estimating the current supplied to a consumer 
by counting the number of hours each lamp is in service. 

To convert lamp-hours to ivatt-hours multiply the number 
of lamp-hours by the number of watts per lamp. The watt- 
hours, divided by 746, will then give the electrical horse-power 
hours. (See Watt-Hours.) 

Lamp, Incandescent Electric An electric 

lamp in which the light is produced by the electric incan- 
descence of a strip or filament of some refractory substance, 
generally carbon. 

The carbon strip or filament is usually bent into the form 
of a horseshoe or arc, and placed inside a glass vessel, called 
the lamp chamber. This vessel is exhausted by means of a 
mercury pump, generally to a fairly high vacuum. 

In order to insure the complete removal from the lamp 
chamber of all the air it originally contained, both it and the 
carbon strip that is placed within it are maintained at a high 
temperature during the process of exhaustion. This tempera- 
ture in practice is obtained by sending the current through 
the carbon strip as soon as the air is nearly all removed. 
Towards the end of the pumping operation the current is 
increased so as to raise the carbons to their full brilliancy. 

This latter operation is termed the occluded-gas process, 
and is essential to the successful sealing of an incandescent 
lamp. By its means, a considerable quantity of air or other 
gaseous substances shut up or occluded by the carbon, is 



WORDS, TERMS AND PHRASES. 



371 



driven out of the carbon, which it would be impossible to get 
rid of by the mere operation of pumping. In order to insure 
the success of the operation it is necessary that the heating 
mast take place while the lamp is being exhausted, since 
otherwise the expelled gases would be reabsorbed. (See 
Gases, Occlusion of.) 

The exhaustion continues up to the moment the lamp cham- 
ber is hermetically sealed. 

The lamp chamber is usually hermetically sealed by the 
fusion of the glass, in the manner adopted in 
the sealing of Geissler tubes, or Crooke's radio- 
meters. 

For the preparation of the carbon strip, its 
carbonization, and the flashing of the strip 
see Carbonization, Processes of, and Flashing 
of Carbons, Process for. 

The ends of the carbon strip, or arc, are 
attached to leading-in wires of platinum that, 
pass through the glass walls of the lamp 
chamber, and are fused therein by melting the 
glass around them, in the same manner as are Fig. 266. 

the leading-in wires in Geissler tubes and other similar ap- 
paratus. 

Incandescent lamps are generally connected to the leads or 
circuits, in multiple-arc, or in multiple-series circuits; they 
are, however, sometimes connected to the line in series. (See 
Circuits, Varieties of.) 

In the former case their resistance is comparatively high ; 
in the latter case, comparatively low. 

Incandescent electric lamps assume a variety of different 
forms. One of them is shown in Fig. 266. The lamp 
chamber conforms in general shape to the outline of the 
filament. 

Lamp, Semi-Incandescent Electric An 

electric lamp, in which the light is due to the combined effects 




372 



A DICTIONARY OF ELECTRICAL 



of a voltaic arc, and electric incandescence. In the Reynier 
semi-incandescent lamp, shown in Fig. 267, a thin pencil of 
carbon C, is gently pressed against a block of graphite B. A 
lateral contact is provided at L, through a block of graphite 
I, by means of which the current is conveyed to the lower 
part only of the movable rod C, which part alone is rendered 
incandescent. 
In this lamp the light is due to both the incandescence of 
q the rod C, and to the small arc 

formed at J, between its lower 
end and the contact block B, 
though mainly from the latter. 

L- a t e n t Electricity.— A 

term formerly applied to bound 
electricity. Now in disuse. (See 
Bound, Dissimulated or Dis- 
guised Electricity.) 

Lateral Discharge.— A 

small discharge observed on the 
discharge of a Leyden jar, be- 
tween parts of the jar not in the 
circuit of the main discharge. 

If a charged Leyden jar is 
placed on an insulating stool, and 
is then discharged by the dis- 
charging rod, the lateral discharge is seen as a small spark 
that passes between the outside coating of the jar and a body 
connected with the earth at the moment of the discharge 
through the rod. This lateral discharge is due to a small 
excess of free electricity on the outside, that is not neutralized 
by the opposite charge. 

A lateral discharge is also seen in the sparks that can be 
taken from a conductor in good connection with the earth, by 
holding the hand near the conductor, while it is receiving 




Words, terms and phrases. 373 

large sparks from a powerful machine in operation. These 
discharges are due to induction. 

Lateral Induction. — Induction observed between closely 
approached portions of a circuit, through which the disruptive 
discharge of a Leyden jar is passed as a long spark, thereby 
making the resistance of the circuit high. 

A long copper wire, bent in the form of an open rectangle, 
has its free ends bent near their extremities so as to approach 
each other until but half an inch apart. The extreme end of 
one of the extremities is provided with a metallic ball, and 
the other end connected with the earth. If, now, a Leyden 
jar charge is passed through the wire, by connecting the outer 
coating with the end of the earth connected wire, and holcl- 
ingthe inside coating near the knob, a spark will pass through 
the half inch of air space between the approached portions 
of the circuit. 

This discharge is clue to what was called formerly lateral 
induction. The discharge from the approached parts of the 
wire is probably to be regarded as a branch discharge, or shunt 
current, due to the fact that the accumulated resistance of 
the wire to the current of the disruptive discharge, becomes 
greater than that of the air space between the approached 
pails of the wire. 

Law, Natural — A correct expression of the 

order in which the causes and effects of natural phenomena 
follow one another. 

The law of gravitation, for example, correctly expresses the 
order of sequence of the phenomena which result when unsup- 
ported bodies fall to the earth. It should be carefully borne 
in mind, however, that natural laws cannot be regarded as 
explaining the ultimate causes of natural phenomena, but 
merely express their order of occurrence or sequence. 

We are, ignorant, for example, of the true cause of gravita- 
tion and are only acquainted with its effects. This is true of 



374 A DICTIONARY OF ELECTRICAL 

all ultimate physical causes, save for the belief in their origin 
in a Divine will. 

Laws, Ampere's or Laws of Electro-Dyna- 
mic Attraction and Repulsion.— Laws expressing the 
attractions and repulsions of electric circuits on one another. 

Laws, Beequerel's or Laws of Magneto- 
Optic Rotation. — Laws of the magneto-optic rotation of 
the plane of polarization of light. (See Magneto- Optic Rota- 
tion.) 

Laws of Coulomb, or Laws of Electrostatic and 
magnetic Attractions and Repulsions. — Laws for the 
force of attraction and repulsion between charged bodies or 
between magnet poles. 

The fact that the force of electrostatic attraction or repul- 
sion between two charges, is directly proportional to the 
product of the quantities of electricity of the two charges and 
inversely proportional to the square of the distance between 
them, is known as Coulomb' 's Law. Coulomb also ascertained 
that the attractions and repulsions between magnet poles is 
directly proportional to the product of the strength of the two 
poles, and inversely proportional to the square of the distance 
between them. This is also called Coulomb's Law. 

Laws of Faraday, or Laws of Electrolysis.— Laws 

for the effects of electrolytic decomposition. (See Electrolysis.) 

Law* of Kirchoff, or Laws of Shunt-Circuits.— 

The laws of branched or shunted circuits. 

These laws may be expressed as follows : 

(1) In any number of conductors meeting at a point, if cur- 
rents flowing to the point be considered as -f-, and those flow- 
ing away from it as — , the algebraic sum of the meeting cur- 
rents will be zero. 

This is the same thing as saying as much electricity must 
flow away from the point as flows toward it. 



WORDS, TERMS AXD PHRASES. 375 

(2) In any system of closed circuits the algebraic sura of the 
products of the currents into the resistances is equal to the 
electro-motive force in the circuit. 

Iu this case all currents flowing in a certain direction are 
taken as positive, and those flowing in the opposite direction 
as negative. All electro-motive forces tending to produce 
currents in the direction of the positive current are taken as 
positive, and those tending to produce currents in the oppo- 
site direction, as negative. 

E 

This follows from Ohm's law; for, since C = — , the electro- 

R 
motive force E = CR, and this is true no matter now often 
the circuit is branched. 

Laws of Lenz. — Laws for determining the directions of 
the cm-rents produced by electro magnetic or electro dynamic 
induction. (See Lenz's Lair.) 

Law of Ohm, or Law for Current Strength.— A 

fundamental law for determining the current strength in any 
circuit. 

The strength of the current in any circuit is directly pro- 
portional to the electro-motive force, and inversely propor- 
tional to the resistance of the circuit. 
E 

C = — , or E = C R. (See Ohm's Laiv.) 
R 

Law of Volta, or Law for Contact-Series.— A law 
for the differences of electric potential produced by the con- 
tact of dissimilar metals or other substances. 

" The difference of potential between any two metals is 
equal to the sum of the differences of potential between the 
intervening substances in the contact-series.''' (See Contact 
Electricity. Contact-Series.) 

Layer, Crookes' A layer, or stratum, in the 

residual atmosphere of a vacuous space, in which the mole- 
cules recoiling from a heated or electrified surface do not 



376 A DICTIONARY OF ELECTRICAL 

meet other molecules, but impinge on the walls of the vessel 
directly opposite to such heated surface. 

A Crookes' layer may result as the effect of two different 
causes, viz. : 

(1) The rarefaction of the gas is such that the distance be- 
tween the walls of the vessel and the heated surface is less 
than the mean free path of the molecules. 

(2) The wall is so near the heated surface that the distance 
between the two is less than the actual mean free path of the 
molecules. Under these last named circumstances, Crookes' 
layers may result whatever be the density of the gas. 

Lead of Brus1ie§ of Dynamo-Electric Machine. 
(See Angle of Lead.) 

Leading Horns of Dynamo-Electric Machine. 
(See Horns, Leading, of Dynamo Electric Machine.) 

Leads. — The main conductors of any system of electric dis- 
tribution. 

The leads, or main conductors in a multiple system of incan- 
descent lighting, must maintain a constant potential at the 
lamp terminals. The dimensions of the leads are therefore so 
proportioned as to absorb as small an amount of potential as 
possible. Since in incandescent lighting, where the lamp is 
connected to the leads in multiple-arc, the total resistance of 
the lamps is comparatively small, the resistance of the leads 
must necessarily be quite small in order to avoid a marked 
drop of potential. Comparatively large conductors must 
therefore be used. 

The main conductor for series circuits, such as for arc lights, 
has in all parts the same current strength. Since the resist- 
ance of the lamp in such a circuit is quite high, a compara- 
tively high resistance in the conductor can be employed with- 
out a proportionally large absorption of potential. Com- 
paratively small conductors can therefore be used. (See Sys- 
tems of Current Distribution by Constant and by Alternating 
Currents.) 



WORDS, TERMS AND PHRASES. 377 

Leakage, Electric The gradual dissipation of a 

charge or current due to insufficient insulation. 

Some leakage occurs under nearly all circumstances. On 
telegraph lines, during wet weather the leakage is often so 
great as to interfere with the proper working of the lines. 

The leakage of a well insulated conductor, placed in a high 
vacuum, is almost inappreciable. Crookes has maintained 
electric charges in his high vacua for years without appre- 
ciable loss. 

Leakage Conductor. — A conductor placed on a tele- 
graph circuit, to prevent the disturbing effects of leakage into 
a neighboring line by providing a direct path for such leakage 
to the earth. 

The leakage conductor, as devised by Varley, consists of a 
thick Avire attached to the pole. The lower end of the con- 
ductor is well grounded, and its upper end projects above the 
top of the pole. 

There exists some doubt in the minds of experienced tele- 
graph engineers whether it is well to apply leakage conductors 
to telegraphic or telephonic lines of over 12 or 15 miles in 
length, since such conductors greatly increase the electro- 
static capacity of the line, and thus cause serious retardation. 

Leakage, Magnetic A useless dissipation of 

the lines of magnetic force of a dynamo-electric machine, or 
other similar device, by their failure to pass through the 
armature. (See Magnetophone.) 

Leclanche'§ Voltaic Cell. (See Cell, Voltaic.) 
Legal Ohm. — The resistance of a column of mercury 
one square millimetre in cross-section and 106 centimetres in 
length, at the temperature of 0° C. or 32° F. (See B. A. Unit.) 
1 Ohm = 1.00112 B. A. Unit. This value of the ohm was 
adopted by the International Electric Congress, in 1884, as a 
value that should be accepted internationally as the true 
value of the ohm. 



B78 A DICTIONARY OF ELECTRICAL 

Length of Spark.— The length of spark that passes 
between two charged conductors depends : 

(1) On the difference of potential between them. 

(2) On the character of the gaseous medium that separates 
the two conductors. 

(3) On the density or pressure of the gaseous medium be- 
tween the conductors. Up to a certain pressure, a decrease 
in the density causes an increase in the length of the distance 
the spark will pass. When this limit is reached, a farther 
decrease of density decreases the length of spark. A high 
vacuum prevents the passage of a spark even under great 
differences of potential. 

(4) On the kind of material that forms the electrodes be- 
tween which the charges pass. 

(5) On the shape of the charged conductor. 

(6) On the direction of the current. Sparks from the prime 
conductor are denser and more powerful than those from the 
negative conductor. 

It will be observed that the length of the spark practically 
depends mainly on two circumstances, viz., on the differences 
of potential of the opposite charges, and the conducting 
power of the medium that separates the two bodies. 

Lenz' Law. — The direction of the currents set up by 
electro-mag'netic induction is always such as to tend to op- 
pose the motion producing them. 

Letter-Boxes, Electric Various devices that 

announce the deposit of a letter in a box, by the ringing of a 
bell or the movement of a needle or index. 

These devices generally act by the making or opening of an 
electric circuit by the fall of the letter in the box. 

Ley den Jar. (See Jar, Ley den.) 

Ley den- Jar Battery. (See Battery, Ley den Jar.) 

Lichtenberg's Figures. (See Figures, Lichteriberg.) 



WORDS, TERMS AND PHRASES. 379 

Life of Electric Incandescent Lamps. — The num- 
ber of hours that an incandescent electric lamp, when traversed 
by the normal current, will continue to afford a good com- 
mercial light. 

The failure of an electric incandescent lamp results either 
from the volatilization or rupture of the carbon conductor, or 
from the failure of the vacuum of the lamp chamber. Since 
the employment of the flashing' process, and the process for 
removing the occluded gases it is not unusual for incandes- 
cent lamps to have a life of several thousand hours. (See 
Flashing Carbons, Process for.) 

Light, Electro-Magnetic Hypothesis of A 

hypothesis for the cause of light proposed by Maxwell, based 
on the relations existing between the phenomena of light 
and those of electro-magnetism. 

Maxwell's electro-magnetic theory of light assumes that 
the phenomena of light and magnetism are each due to cer- 
tain motions of the ether. Electricity and magnetism being 
due to its rotations or oscillations, and light to its to-and-fro 
motions. 

He proposed this theory to show that the phenomena of 
light, heat, electricity and magnetism could all be explained 
by one and the same cause, viz., a vibratory or oscillatory 
motion of the particles of the hypothetical ether. Maxwell 
died before completing his hypothesis, and it has never since 
been sufficiently developed to thoroughly entitle it to the 
name of a theory. 

There are, however, numerous considerations which render it 
probable that electric and magnetic phenomena, like those of 
light and heat, have their origin in a vibratory or oscillatory 
motion of the luminiferous ether. A few of these, as pointed 
out by Maxwell, S. P. Thompson, Lodge, Larden and others, 
are as follows : 

(1) It is quite possible that the thing called electricity is the 
ether itself ; negative electrification consisting in an excess of 



880 A DICTIONARY OF ELECTRICAL 

the ether, and positive electrification in a deficit. (See Hy- 
potheses of Electricity.) 

(2) It is possible that electrostatic phenomena consist in a 
strain or deformation of the ether. A dielectric may differ 
from a conductor in that the former may have such an attrac- 
tion for the ether as to give it the properties of an elastic 
solid, while in the latter the ether is so free to move that no 
strain can possibly be retained by it. (See Dielectric. Con- 
ductor.) 

(3) Dielectrics are transparent and conductors are opaque. 
There are exceptions to this in the case of vulcanite and 

man} T other excellent dielectrics. Nor should this similarity 
be expected to be general in view of the difference between 
diathermancy and transparency. 

(4) It is possible that an electric current consists of a real 
motion of translation of the ether through a conductor. 

(5) It is possible that electro-motive force results as differ- 
ences of ether pressures, this would of course follow from (4). 

(6) The vibrations of light are propagated in a direction at 
right angles to the direction in which the light is moving. 
The magnetic field of a current is propagated in planes at 
right angles to the direction in which the current is flowing. 

(7) It is possible that lines of electrostatic and magnetic 
force consist of chains of polarized ether particles. 

(8) The velocity of propagation of light agrees very nearly 
with the velocity of propagation of electro-magnetic induc- 
tion. (See Velocity Ratio.) 

(9) In certain axial crystals the difference of transparency 
in the direction of certain axes, corresponds with the direc- 
tion in which such crystals conduct electricity. 

Light-House Illumination, Electric 

The application of the electric arc light to the 

illumination of light houses. 

A powerful arc light is placed in the focus of the dioptric 
lens now commonly employed in light houses. Since the con- 



WORDS, TERMS AND PHRASES. 331 

sumption of the carbon electrodes would alter the position 
of the focus of the light, electric lamps for such purposes are 
constructed to feed both of their carbons instead of the upper 
carbon only, as in the case of the ordinary arc lamp. 

Light, Intensity oi* (See Intensity of Light. 

Photometer.) 

Lighting, Central Station The lighting of a 

number of houses or other buildings from a single station, 
centrally located. 

Central station lighting is distinguished from isolated 
lighting, by the fact that a number of separate buildings, 
houses, or areas are lighted by the current produced at a 
single station, centrally located, instead of from a number of 
separate electric sources located in each of the houses, etc., 
to be lighted. (See Systems of Electric Distribution.) 

Lightning.— The spark or bolt that results from the dis- 
charge of a cloud to the earth, or to a neighboring cloud. 
(See Atmospheric Electricity. Kite, Franklin's.) 

Lightning Arrester.— A device, by means of which the 
apparatus placed in any electric circuit are protected from 
the destructive effects of a flash or bolt of lightning. 

In the phenomena of lateral induction we have seen the 
tendency of a disruptive discharge to take a short cut across 
an intervening air space, rather than through a longer though 
better conducting path. Most lightning arresters are depend- 
ent for their operation on this tendency to lateral discharge. 
(See Induction, Lateral. Discharge, Disruptive.) 

A form of lightning arrester is shown in Fig. 268. 

The line wires A and B, are connected by two metallic plates 
to C and D, respectively. 

These plates are provided with points, as shown, and placed 
near a third plate, connected to the ground by the wire G. 
Should a bolt strike the line, it is discharged to the earth 
through the wire G, 



A DICTIONARY OF ELECTRICAL 



Lightning, Back or Return Stroke.— (See Back or 
Return Stroke of Lightning.) 

Lightning, Globular A rare form of light- 
ning, in which a globe of fire appears for a while, quietly 
floats in the air, and then explodes with great violence. 

The exact cause of globular lightning is unknown. Phe- 
nomena allied to it, however, have been observed by Plants 
during the discharge of his rheostatic machine, when dis- 
charged in series, or for a great difference of electric potential. 
Similar phenomena, are sometimes, though rarely, observed 
during the discharge of a powerful Leyden battery. Sir Wm. 
Thomson ascribes the effect to an optical illusion. 




.Lightning, Heat or Sheet, Volcanic and Zigzag 

Heat or sheet lightning is the name given to a dis- 



charge unaccompanied by any thunder audible to the observer, 
in which the entire surfaces of the clouds are illumined. 

Its cause has been ascribed to the reflection from the clouds 
of lightning flashes too far below the horizon to permit them 
to be directly seen, or the thunder to be audible, 



WORDS, TERMS AND PHRASES. 383 

If a Geissler tube, which contains several concentric tubes, 
be charged by a Holtz machine, and then touched at different 
parts by the hands, a succession of luminous discharges will 
be seen in the dark, that bear a remarkable resemblance to 
the flashes of heat or sheet lightning. 

Lightning Rods. — A rod, or wire cable of good conduct- 
ing material, placed on the outside of a house or other struc- 
ture,^ order to protect it from the effects of a lightning dis- 
charge. 

Lightning rods were invented by Franklin. The result of a 
very extended inquiry recently made on the subject, leaves no 
room for doubt that a lightning rod, properly constructed and 
placed, affords an efficient protection to the buildings on 
which it is placed. 

To insure this protection, however, all the following con- 
ditions must be carefully fulfilled, else the rod may prove a 
source of danger rather than a protection, viz.: 

(1) The rod, generally of iron or copper, should have 
such an area of cross section as to enable it to cany without 
fusion the heaviest bolt it is liable to receive in the latitude 
in which it is located. When of iron, the area of cross 
section should be about seven times greater than when of 
copper. 

(2) The rod should be continuous throughout, all joints being 
carefully avoided. If these be used they should be made of as 
low resistance as possible and should be protected against 
corrosion. 

(3) The upper extremity of the rod should terminate in one 
or more points formed of some metal that is not readily cor- 
roded, such as platinum or nickel. 

(4) The lower end of the rod should be carried down into 
the earth until it meets permanently damp or moist ground, 
where it should be attached to a fairly extended metallic sur- 
face buried in the ground. Metallic plates will answer for the 
purpose, but, if gas or water pipes are available, the rod should 



384 A DICTIONARY OF ELECTRICAL 

be placed in good electrical connection therewith, by wrapping 
it around and soldering it to such pipes. 

This fourth requirement is of great importance to the pro- 
per action of a lightning rod, and unless thoroughly fulfilled 
may render the rod worthless, no matter how carefully the other 
requirements are attended to. When a bolt strikes a light- 
ning rod which is not properly grounded, the discharge is almost 
certain to destroy the building to which the rod is connected. 

(5) The rod should not be insulated from the building, un- 
less to prevent stains from the oxidation of the metal. On the 
contrary it should be directly connected with all masses of metal 
in its path, such as tin roofs, gutter-spouts, metallic cornices, 
etc. In this way only can dangerous disruptive lateral dis- 
charges from the rod to such masses of metal be avoided. 

(6) The rod should project above the roof or highest part of 
the building, or, in other words, the height of the rod should 
bear a certain proportion to the size of the building to be pro- 
tected. A rod will protect a conical space around it, the 
radius of whose base is equal to the vertical height of the rod 
above the ground, but whose sides are curved inwards instead 
of being straight. Where the building is very high, a num- 
ber of separate rods all connected to one another should be 
employed. 

(7) A stranded conductor is much better than an equal cross 
section of a solid rod of the same metal. 

A lightning rod more frequently acts to quietly discharge 
an impending cloud by convective discharge, than by an ac- 
tual disruptive discharge of the same. (See Discharge, Con- 
vective. Discharge, Disruptive.) 

Lightning rods should be frequently tested to see that no 
breaks or oxidation of their joints have occurred. 

Lightning Rods for Ships.— A system of rods designed 
to afford electric protection for vessels at sea. 

Since the lightning discharge takes place between the 
points of greatest difference of potential, and these are gener- 



WORDS, TERMS AND PHRASES. 385 

ally between the cloud and the nearest point of the earth, tall 
objects are especially liable to be struck. 

Ships at sea should, therefore, be thoroughly protected from 
lightning. 

In Harris' system of lightning protection for ships, the rods 
are connected with a series of copper plates and rods so placed 
on the masts as to readily yield to strains. These are elec- 
trically connected with the copper sheathing of the vessel and 
with all large masses of metal in the vessel. This latter precau- 
tion is especially necessary in the case of men-of-war, in order 
to protect the powder magazine. Harris' method for the light- 
ning protection of ships, which was adopted only after very 
considerable opposition, proved so efficacious in practice that 
serious effects of lightning on vessels so protected are now 
almost unknown. In 1845, Harris received the honor of 
knighthood from the English Government for his services in 
this respect. 

A lightning rod sometimes fails to protect a house or barn 
from the fact that a heated, ascending current of air from a 
fire in the house, or from the gradual heating of green hay or 
grain in the barn, increases the virtual height of the house 
beyond the ability of its rod to protect it. 

Lightning, Volcanic — The lightning dis- 
charges that attend most volcanic eruptions. 

Volcanic lightning is probably due to the friction of volcanic 
dust particles against one another, or against the air, but par- 
ticularly to the sudden condensation of the vapor that is gen- 
erally disengaged during volcanic eruptions. 



Lightning, Zigzag, Chain or Forked 



The commonest variety of lightning flashes in which the dis- 
charge apparently assumes a forked zigzag, or even a chain- 
shaped path. 

This form is seen in the discharge of a Holtz machine, or of 
a Ruhmkorff Induction Coil. 



d»b A DICTIONARY OF ELECTRICAL 

The irregular shape of the path is probably due to the 
resistance of solid particles in the air, which are piled up in 
front of the discharge, or to the effects of the lateral induc- 
tion that is produced during the discharge. (See Induction, 
Lateral.) 

Line, Neutral of a Magnet.— A line joining the 

neutral points of a magnet, or the points approximately mid- 
way between the poles. 

This is sometimes called the equator of the magnet. 

The neutral point is the point where the lines of force out- 
side the magnet are parallel to the surface of the magnet. 
(Hering.) 

Line, Neutral of Commutator Cylinder.— A 

line on the commutator cylinder of a dynamo-electric machine, 
connecting the neutral points, or the points of maximum posi- 
tive and negative difference of potential. (See Dynamo- 
Electric Machine.) 

Line, Telegraphic, Telephonic, etc. The 

conducting circuit provided for the transmission of the elec- 
tric impulses or currents employed in any system of electric 
transmission. 

Lines, Aclinic, or Isoclinic Lines connecting 

places that have the same magnetic inclination. (See Aclinic 
Line. Isoclinic Line.) 

Lines, Agonic, or Isogonic Lines connecting 

places that have an equal magnetic declination. (See A gone.) 

Lines, Isodynamic (See Isodynamic Lines.) 

Lines of Electrostatic Force. — Lines extending in the 
direction in which the force of electrostatic attraction or re- 
pulsion acts. 

Lines of electrostatic force pass through dielectrics; whether 
the force acts by means of a polarization of the dielectric, or 
by means of a tension set up in it, is not known. (See Field, 
Electrotastic.) 



WORDS, TERMS AND PHRASES. 387 

Lines of Force, Direction of Lines 

extending in the direction in which the lines of magnetic force 
are assumed to pass. 

The lines of magnetic force are assumed to come out of the 
north pole of a magnet, and to pass in at its south pole. 

The lines of electrostatic force are assumed to pass out of a 
positively charged surface, and into a negatively charged sur- 
face. 

Lilies of Magnetic Force.— Lines extending in the 
direction in which the force of magnetic attraction or repul- 
sion acts. (See Field, Magnetic.) 

Liquids, Specific Resistance of The resist- 
ance of a given length (one centimetre) and cross section (one 
square centimetre) of any liquid as compared with the resist- 
ance of an equal length and cross section of pure silver. 
The resistance of a few common liquids and solutions is here 
given from Lupton : 
Water, pure at 75° C 1.188 X 10 8 ohms 

i. e., 118,800,000. 

Water at 4° C 9.100 X 10 6 " 

Water at 11° C 3.400 X 10 5 " 

Dilute hydrogen sulphate (sulphuric acid) at 

18° C. 5 per cent, acid 4.88 

Dilute hydrogen sulphate at 18° C. 3 per 

cent.acid 1.38 " 

Nitric acid, at 18° C. density 1.32 1.61 " 

Saturated solution of copper sulphate (blue 

vitriol) at 10° C 29.30 

Saturated solution of zinc sulphate at 14° C. 21.50 " 

Hydrochloric acid, 20 per cent, acid, at 18° C. 1.34 " 

Sal ammoniac, 25 per cent, salt 2.53 " 

Common salt, saturated, at 13° C 5.30 " 

It will be observed that the resistance varies considerably 
with differences of temperature. 



388 A DICTIONARY OF ELECTRICAL 

Local Action. — In a battery, the loss of energy by the 
irregular and wasteful solution of the zinc or positive element 
by the electrolyte. 

The local action of a battery is caused by the solution of the 
zinc or positive plate by the action of local voltaic couples 
formed by couples of zinc and minute particles of carbon, lead, 
or other impurities. It is remedied by the amalgamation of 
the zinc. (See Zinc, Amalgamation of.) 

In a dynamo electric machine, the loss of energy by the 
setting up of eddy currents in the conducting masses of the 
pole-pieces, cores, etc. (See Currents, Eddy.) 

In a dynamo electric machine local action is obviated by a 
lamination of the pole pieces, armature core, etc. (See 
Lamination of Cores. ) 

Local Battery. — (See Battery, Local.) 

Local Currents. — (See Currents, Eddy.) 

Localization of Faults. — Determining the position of 
a fault in a telegraph line or cable by calculations based on the 
fall in the potential of the line measured at different points 
or by loss of charge, etc. 

For description see standard works. 

Locomotive, Electric A railway engine whose 

motive power is electricity. (See Railroad Electric.) 

Locomotive Head-Light, Electric (See 

Head-Light, Electric.) 

Lodes tone. — A name applied by the ancients to an ore 
of iron (magnetic iron ore), that naturally possesses the power 
of attracting light pieces of iron to it. 

Lodestone, or magnetic iron ore, must be regarded as a 
magetizable substance that has become permanently magnetic 
from its situation in the earth's magnetic field. Such beds of 
ore concentrate the lines of the earth's magnetic field on them, 
and thus become magnetic. 



WORDS, TEHMS AND PHRASES. 389 

Log, Electric An electric device for measuring 

the speed of a vessel. 

Any log- that operates by the rotation of a wheel is caused 
to register the number of rotations by a step-by-step recording- 
apparatus operated by breaks in the circuit, made during- the 
rotation of the wheels, at any given number of turns, say 100, 
or any other convenient multiple. Such a log* may he kept 
constantly in the water, and observed when required, or it can 
be made to register a permanent record of its actual speed at 
any lime during the entire run. 

Logarithm*. — The logarithm of any given number, is the 
exponent of the power to which it is necessary to raise a fixed 
number, in order to produce the given number. 

A table of logarithms enables the operations of multiplica- 
tion, division, and the extraction of roots, to be readily per- 
formed by simple multiplication, division, addition or subtrac- 
tion. When thoroughly understood, logarithms greatly re- 
duce the labor of mathematical calculations. For the manner 
in which they are used the student is referred to any standand 
work on mathematics. 

Longitude, Electrical Determination of 



The determination of the longitude of a place, by differ- 
ences in time between it and a place on the prime meridian, as 
simultaneously determi ned telegraphically. 

In determinations of this character allowance must be made 
for the retarding effects of long telegraphic lines, or cables. 

Loop, Electric A portion of a main circuit 

consisting of a wire going out from one side of a break in the 
main circuit and returning to the other side in the break. 

Loops are employed for the purpose of connecting a branch 
telegraph office with the main line ; for placing* one or more 
electric arc lamps on the main line circuit ; for connecting a 
messenger call, or telephone circuit with a main line; and for 
numerous similar purposes. 



390 



A DICTIONARY OF ELECTRICAL 



Loxodrograpn. — An apparatus for electrically recording 1 
on paper the actual course of a ship by the combined action of 
magnetism and photography. 

Luces. — Plural of lux. (See Lux.) 

Lux. — A name proposed by Preece for the unit of inten- 
sity of illumination. 

One lux is the illumination given by a standard candle at the 
distance of 12.7 inches. 

One lux is the illumination given by a carcel at the distance 
of one metre. 

One lux is the illumination given by a lamp of 1,000 candles 
at 105.8 feet. (See Illumination, Unit of.) 



Machine, Frictional Electric 

A machine for the de- 
velopment of electric- 
ity by friction. 

A frictional electric 
machine consists of a 
plate or cylinder of 
glass A, Fig. 271, ca- 
pable of rotation on a 
horizontal axis. 

A rubber formed of a 
chamois skin, covered 
with an amalgam of tin 
and mercury, is placed 
at B. By the rotation 
of the plate the rubber becomes negatively, and the glass 
positively excited. An insulated conductor D, called the 
prime or positive conductor, provided with a comb of points, 
becomes positively charged by induction. The machine 
will develop electricity best if a conductor attached to the 




271. 



WORDS, TERMS AND PHRASES. 



391 



rubber is connected with the ground, as by a chain, as 
shown. 

Machines, Electrostatic Induction 



or Influence Machines. — Machines in which a small 
initial charge produces a greatly increased charge by its in- 
ductive action on a rapidly rotated disc of glass. 

An excellent type and example of such a machine is found 
in the Holtz machine which consists of the following parts, 
as shown in Fig. 272, viz. : 

(1) A stationary glass plate A, fixed at its edges to insulated 
supports. 

(2) A movable plate B, capable of rapid rotation on a hor- 
izontal axis, by a driv- 
ing pulley. 

(3) Armatures of var- 
n i s h e d paper/,/', 
placed on opposite sides 
of the fixed plate at 
holes or windows P, P', 
cut in the plate. The 
armatures are placed 
on the side of the fixed 
plate away from the 
moving plate, or on the 
back of the plate, so 
that the plate, on its 
rotation, moves towards tongues of paper attached to the 
middle of the armature. 

(4) Metal combs placed in front of the movable disc oppo- 
site the armatures, and connected with the brass balls m, n, 
one of which is movable towards and from the other by 
means of a suitably supported insulating- handle connected 
with it. 




892 A DICTIONARY OP ELECTRICAL 

A small initial charge is given to one of the armatures by 
holding a plate of electrified vulcanite on it, and rotating the 
machine while the balls m, n, are in contact. As soon as the 
machine is charged the balls are gradually separated, when a 
torrent of sparks will pass between them so long as the plate 
is rotated. 

When the balls are separated too far the sparks cease to 
pass. The balls must then be again brought into contact and 
gradually separated as before. 

The Holtz machine can be regarded as a revolving electro- 
phones provided with means for constantly discharging and 
recharging the upper metallic plate. (See Electrophorus). 

The action of the machine is well described by S. P. Thomp- 
son in his " Elementary Lessons on Electricity and Magnetism," 
as follows : 

' ' Suppose a small -f- charge to be imparted at the outset to 
the right armature /; this charge acts inductively across the 
discs upon the metallic comb, repels electricity through it, 
and leaves the points negatively electrified. They discharge 
negatively electrified air upon the front surface of the mov- 
able disc ; the repelled charge passes through the brass rods 
and balls, and is discharged through the left comb upon the 
front side of the movable disc. Here it acts inductively upon 
the paper armature, causing that part of it which is opposite 
itself to be negatively charged and repelling a -f- charge into its 
farthest part, viz., into the tongue, which being" bluntly 
pointed, slowly discharges a -j- charge upon the back of the 
movable disc. If now the disc be turned round, this -|- charge 
on the back comes over from the left to the right side, in the 
direction indicated by the arrow, and, when it gets opposite 
the comb, increases the inductive effect of the already existing 
-f- charge on the armature, and therefore repels more electricity 
through the brass rods and knobs into the left comb. Mean- 
time the — charge, which we saw had been induced in the left 



WORDS, TERMS AND PHRASES. 




armature, has in turn acted on the left comb, causing a -\- 
charge to be discharged by the points upon the front of the disc ; 
and, drawing electricity through the brass rods and knobs, has 
made the right comb still more highly — , increasing the dis- 
charge of — ly electrified air upon the front of the disc, neu- 
tralizing the -f- charge 
w hi c h is being con- 
veyed over from the 
left. These actions re- 
sult in causing the top 
half of the moving - disc 
to be — ly electrified. 
The charges on the 
front serve as they are 
carried round, to neu- 
tralize the electricities 
let off by the points of 
tht» combs, while the 
charges on the back, in- Fi 0- -75. 

duced respectively in the neighborhood of each of the arma- 
tures, serve, when the rotation of the disc conveys them 
round, to increase the inductive influence of the charge on 
the other armature." 

The student will be aided in following Prof. T.s explanation 
by the diagrammatic sketch, shown in Fig. 273. Here the rotat- 
ing plate is shown for convenience in the form of a cylinder. 
The armatures are shown on the back of the plate at /' and/, 
opposite the brass collecting combs P' and P, with their dis- 
charging rods and balls a a. 

The effect of the positive charge given to the right hand 
armature/, directly through the combs P , rods a a, comb P, 
to left hand armature /, is readily seen. The rotation of 
the plate being In the direction of the curved arrows, the 
charging of the front of the plate by convection streams 
from the combs, and the back of the plate from the points 



394 A DICTIONARY Off ELECTRICAL 

of the paper armatures, as well as the character of the 
charge will he understood. There thus results, as is shown, 
a positive charge on both the front and back of the upper 
half of the rotating plate, and a negative charge on both 
sides of its lower half. A reversal of polarity of the plate 
occurs at the line PaaF, Sometimes the reversal does not 
occur and the machine either loses its charge entirely, or 
in part. A conductor S S, furnished with points, is sometimes 
provided to lessen the chances of lack of reversal. 

Machines, Faradic (See Faradic Machines.) 

Made Circuit.— (See Circuit, Closed.) 

Magnc-Crystallic Action. — A term proposed by Fara- 
day to express the differences in the action of magnetism on 
ciystalline bodies in different directions. 

A needle of tourmaline if hung with its axis horizontal is no 
longer paramagnetic as usual, but diamagnetic. The same is 
true of a crystal of bismuth. Faraday concluded from these 
experiments that a force existed distinct from the paramag- 
netic or diamagnetic force. He called this the magne-crys- 
tallic force. 

Plucker infers from these phenomena that a definite relation 
exists between the ultimate form of the particles of matter 
and their magnetic behavior. The subject may be regarded 
as yet somewhat obscure. (See Diamagnetic Polarity.) 

Magnet. — A bod}' possessing the power of attracting the 
unlike poles of another magnet or repelling the like poles ; or 
of attracting readily magnetizable bodies like iron filing's to 
either pole. 
A body possessing a magnetic field. — (See Field, Magnetic.) 
The lines of force are assumed to pass through the magnetic 
field out at the north pole and in at the south pole. All lines of 
force form closed magnetic circuits. If a magnetizable body 
is brought into a magnetic field, the lines of magnetic force 



WORDS, TERMS AND PHRASES. 395 

are concentrated on it and pass through it. The body there- 
fore becomes magnetic. The intensity of the resulting 
magnetism depends on the number of lines of force that pass 
through the body, and the polarity on the direction in which 
they pass through it. 

Magnet, V nomalou§ A magnet which pos- 
sesses more than two poles. — (See Anomalous Magnet.) 

Magnet, Artificial A magnet produced by 

induction from another magnet, or from an electric current. 

Any magnet not found in nature is called an artificial 
magnet. 

Magnet, Bell Shaped A modification of a 

horseshoe shaped magnet in which the approached poles are 
semi-annular in shape, and form a split tube. 

Bell magnets are. used in many galvanometers, because they 
can be readily dampened by surrounding them by a mass of 
copper. The needle in its motion produces currents that 
tend to oppose and therefore to stop its motion. (See Lenz's 
Law.) 

Magnet Coils. — The coils of insulated wire surrounding" 
the core of an electro magnet, and through which the mag- 
netizing current is passed. — (See Magnetism, Ampere's Theory 
of. Dynamo Electric Machine, Field Magnets.) 

Magnet, Compensating — —A magnet placed 

over a magnetic needle, generally over the magnetic needle 
of a galvanometer, for the purpose of varying the direction 
and intensity of the magnetic force of the earth on the 
needle. — (See Galvanometer, Reflecting.) 

A magnet, called a compensating magnet, is sometimes placed 
on a ship, near the compass needle, for the purpose of neutral- 
izing the local variation produced on the compass needle by 
the magnetism of the ship. 



896 



A DICTIONARY OF* ELECTRICAL 



Magnet, Compound 



•A number of single 



magnets, placed parallel and with their similar poles facing 
one another, as shown in Fig. 274. 

Compound magnets are stronger in proportion to their 
weight than single magnets. 

Magnet, Electro A magnet produced by the 

passage of an electric current around a core of soft iron.— (See 
Electro-Magnet. ) 

Magnet, Horse§lioe (See 

Horseshoe Magnet.) 

Magnet, Keeper of (See 

Keeper of Magnet. ) 

Magnet, Permanent A 

magnet of hardened steel or other sub- 
stance which retains its magnetism for a 
long time after being magnetized. 

A permanent magnet is distinguished, 
in this respect, from a temporary magnet 
of soft iron which loses its magnetization 
very shortly after being taken from the 
magnetizing- field. 



NkZ= 




Magnet, Portative Power of 

°' 27lt ' The lifting power of a magnet. 

The portative, or lifting power of a magnet, depends on the 
form of the magnet, as well as on its strength. A horseshoe 
magnet, for example, will lift a much greater weight than 
the same magnet if in the form of a straight bar. 

This is due not only to the mutual action of the approached 
poles, but also to the decreased resistance of the magnetic 
circuit, and to the greater number of lines of magnetic force 
that pass through the armature. 

The portative power increases as the area of contact in- 
creases. 



Magnet, Receiving 



or Relay. — (See Relay.) 



WORDS, TERMS AND PHRASES. 397 

Magnet, Simple A single magnetized bar. 

Magnet, Solenoidal A long, thin, uniformly 

magnetized straight bar of steel, with its poles at its extremi- 
ties, that acts on external objects as if equal and opposite quan- 
ties of magnetism were collected at its extremities. 

It derives its name solenoidal, from the similarity between 
its action and that of a solenoid. Unless very carefully mag- 
netized a magnet will not act as a solenoidal magnet. (See 
Electro-Magnet. Solenoidal Distribution of Magnetism. ) 

Magnet, Tubular or Iron-Clad Magnet. — 

A form of horseshoe magnet in which one pole is brought 
near the opposite pole by a hollow cylinder or tube, which is 
placed in contact with one of the magnetic poles, so as to 
completely surround the other, except in the plane of cross 
section of that pole. 

There is thus obtained a magnet, with two concentric poles, 
one solid and one annular, the portative power of which is 
much greater than that of a horseshoe magnet of equal di- 
mensions. 

Magnetic Attraction. — (See Attraction, Magnetic.) 

Magnetic Axis. — (See Axis, Magnetic.) 

Magnetic Azimuth.— (See Azimuth, Magnetic.) 

Magnetic Battery. — (See Battery, Magnetic.) 

Magnetic Bridge.— (See Bridge, Magnetic.) 

Magnetic Circuit. — (See Circuit, Magnetic.) 

Magnetic Couple.— (See Couple, Magnetic.) 

Magnetic Curves. — Curved lines, formed by sprinkling 
iron filings on a sheet of paper or glass held in the field of a 
magnet, and gently tapping the same so as to permit the fil- 
ings to arrange themselves in the direction of the lines of 
magnetic force. (See Figures, Magnetic.) 



OVO A DICTIONARY OF ELECTRICAL 

Magnetic Declination.— The angular deviation of the 
magnetic needle to the east or west of the true geographical 
north. (See Needle, Declination of. Declination Chart.) 

magnetic Density.— (See Density, Magnetic.) 

Magnetic Dip.— (See Dip, Magnetic.) 

Magnetic Explorer.— (See Explorer, Magnetic.) 

Magnetic Field.— The atmosphere of magnetic influence 
which surrounds the poles of a magnet. 

Any space traversed by lines of magnetic force, forms a 
magnetic field. (See Field, Magnetic.) 

Magnetic Figures.— (See Figures Magnetic. Field, Mag- 
netic.) 

Magnetic Filament.— A polarized line or chain of ulti- 
mate magnetic particles. (See Filament, Magnetic.) 

Magnetic Force. — The force which causes magnetic at- 
tractions and repulsions. 

Magnetic Inclination.— The angular deviation from 
a horizontal position of a freely suspended magnetic needle. 
(See Dip of Needle. Inclination Chart.) 

Magnetic Induction. — The magnetization of magnetiz- 
able substances by bringing them into a magnetic field. (See 
Induction, Magnetic.) 

Magnetic Inertia. — (See Inertia, Magnetic. Lag, 
Magnetic.) 

Magnetic Intensity. — (See Intensity of Magnetiza- 
tion.) 

Magnetic Lag. — (See Lag, Magnetic.) 

Magnetic Leakage. — Useless dissipation of lines of 
magnetic force outside that portion of the field of a dynamo 
electric machine through which the armature moves. 

Magnetic leakage will result in a low efficiency of the dyna- 
mo. (See Coefficient, Economic of Dynamo.) 



WORDS, TERMS AND PHRASES. 399 

Magnetic Lines of Force. — (See Lines of Force, Mag- 
netic.) 

Magnetic Masses. — (See Masses, Magnetic.) 
Magnetic Memory. — A term proposed by J. A. Fleming 
for coercive force. Y 
Soft iron has but a feeble memory of its past magnetization. 
Magnetic Meridian. — The magnetic meridian of any 
place is the meridian which passes through the poles of a mag- 
netic needle, when in a position of rest under the free influence 
of the earth's magnetism at that place. 

The plane of the magnetic meridian of a place is a vertical 
plane passing through the poles of a magnetic needle in a 
position of rest under the free influence of the earth's mag- 
netism at that place. 

Magnetic Moment. — The magnetic moment of a mag- 
netic needle is the product of one of the two forces of the 
directive couple, multiplied by the perpendicular distance be- 
tween the directions of these forces ; or, in other words, the 
moment of a magnet is equal to its length multiplied by the 
intensity of the magnetism of one of its poles. -(See Couple, 
Magnetic). 
Magnetic Observatory. — (See Observatory, Magnetic.) 
Magnetic Permeability. — Conductibility for lines of 
magnetic force. 

Iron is a substance which possesses great magnetic permea- 
bility. When placed in a magnetic field the lines of force 
are concentrated on and readily pass through its mass, or, in 
other words, its magnetic resistance is low. All paramag- 
netic bodies, have a high magnetic permeability. (See Par- 
amagnetic) 

Magnetic Pole§, False (See False Poles, Mag- 
netic.) 

Magnetic Reluctance. — A term recently proposed in 
place of magnetic resistance, to express the resistance offered 



400 A DICTIONARY OF ELECTRICAL 

by a medium to the passage through its mass of the lines of 
magnetic force. 

Magnetism, Residual The small amount of 

magnetism retained by soft iron when removed from a mag- 
netizing field. 

Magnetic Resistance.— Resistance offered by a medium 
to the passage of the lines of magnetic force through it. 

The magnetic resistance of the circuit of the lines of force is 
reduced by forming the circuit of a medium having a high 
magnetic permeability, such as soft iron. This is accomplished 
by the armature or keeper of a magnet, or by the iron in an 
ironclad magnet. (See Iron- Clad Magnet.) 

Magnetic Retentivity.— (See Retentivity, Magnetic.) 

Magnetic Saturation. — The condition of iron, or other 
paramagnetic substance, when its intensity of magnetization is 
so great that it fails to be further magnetized by any magnetic 
force however great. 

When the core of an electro-magnet is saturated by the 
passage of an electric current, the only further increase of its 
magnetization that is possible, is that due to the magnetic 
field of the increased current which may be sent through its 
coils. This is comparatively insignificant. 

A magnet is sometimes said to be super-saturated, that is, 
to have received more magnetism than it can retain for any 
considerable time after its magnetization. 

Magnetic Screen, or Shield. — A hollow box whose 
sides are made of thick iron, placed around a magnet or other 
body so as to cut it off or screen it from any magnetic field 
external to the box. 

Magnetic screens are placed around delicate galvanometers 
to avoid any variations in their field due to extraneous masses 
of iron, or neighboring magnets. They are also sometimes 
placed around watches to shield or screen the works from the 
effects of magnetism. 



WORDS, TERMS AND PHRASES. 401 

To act effectively, when the external fields are at all power- 
ful, magnetic screens must be made of thick iron. They differ 
in this respect from electrostatic shields, which will afford 
protection against electrostatic charges although they may be 
but mere films. (See Shields, Electrostatic.) 

Magnetic Shells. — A sheet or layer consisting of mag- 
netic particles, all of whose north poles are situated in one of 
the flat surfaces of the sheet, and the south poles in the oppo- 
site surface. (See Shell, Magnetic. Lamellar Distribitt ion of 
Magnetism.) 

Magnetic Solenoids. — A spiral coil of wire which acts 
like a magnet when an electric current passes through it. (See 
Solenoids, Electro- Magnetic.) 

Magnetic Sounds. — Faint clicks heard on the magneti- 
zation of a readily magnetizable substance. 

One of the earlier forms of Reis' telephone operated by 
means of a rapid succession of these faint, magnetic sounds. 

Magnetic Storms. — Sudden, but small and irregular 
variations in the intensity of the earth's magnetism that 
simultaneously affect all parts of the earth. 

Magnetic storms have been observed to accompany auroral 
displays, and to be coincident with the occurrence of sun 
sjjots, or unusual outbursts of solar activity. 

Magnetic Susceptibility. — The relation which exists be- 
tween the strength of the magnetizing field and that of the 
magnetized body, or the intensity of the magnetism induced, 
divided by the intensity of the inducing field. 

When the inducing field has unit strength of magnetiza- 
tion the magnetic susceptibility will measure directly the 
strength of the magnetization. 

When a bar of iron is placed in a magnetic field, it is 
threaded by the lines of magnetic force, and thus becomes 
magnetized by induction. This induction will necessarily 



402 A DICTIONARY OF ELECTRICAL 

depend both on the number of lines of force in the magnet- 
izing field, and on the magnetic permeability of the magnet- 
ized body ; or, in other words, the induction is equal to the 
product of the intensity of the magnetizing field and the 
magnetic permeability of the body in which the induction 
occurs. 

Magnetic Variations.— Variations in the value of the 
magnetic declination, or inclination, that occur simultaneously 
over all parts of the earth. 

These variations are : 

(1) Secular, or those occurring at great cycles of time. 

(2) Annual, or those occurring at different seasons of the 
year. 

(3) Diurnal, or those occurring at different hours of the 
day, and, 

(4) Irregular, or those accompanying magnetic storms. The 
first three are periodical ; the last is irregular. (See Angle of 
Declination. Variation Chart. Inclination Chart.) 

Magnetite. — Magnetic oxide of iron, or Fe 3 4 . 

Lodestone consists of pieces of magnetized magnetite. 

Magneto-Electricity. — Electricity produced by the mo- 
tion of magnets past conductors, or of conductors past mag- 
nets. 

Magneto-Electric Call Bell.— An electric call bell 
operated by currents produced by the motion of a coil of wire 
before the poles of a permanent magnet. 

Magneto-Electric Induction. — Electric induction pro- 
duced by the motion of a conductor past a permanent magnet, 
or vice versa. (See Induction, Electro Magnetic.) 

Magneto-Electric Machine. — A dynamo in which 
currents are produced by the motion of armature coils past 
permanent magnets. (See Dynamo Electric Machine.) 

Magnet ograph, or Self-Recording Magnetome- 
ter. — A self-recording apparatus by means of which the daily 



WORDS, TERMS AND PHRASES. 



403 



and hourly variations of the magnetic needle are continuously 
registered. 

The magnetograph, as employed in the observatory at Kew, 
consists essentially of a photographic record of a spot of light 
reflected from a mirror attached to the needle whose varia- 
tions are to be record- 
ed. The photographic 
record is received on 
a strip of sensitized 
paper, maintained in 
uniform and continu- 
ous motion by means 
of suitable clockwork. 
The record so obtained 
is called a magneto- 
graph. 

Magnelomct e r . 

— An apparatus for 
the measurement of 
magnetic force by the 
torsion balance. 

The principles of 
the operation of the 
magnetometer are the 
same as those of the 
torsion balance. (See 
Balance, Coulomb's 
T o r s ion.) A mag- 
net N S, Fig. 275, is 
suspended by a single 
wire, and the magnet FiQ- % 75 - 

N, whose strength is to be measured is introduced in an open- 
ing at the top of the glass cage, in place of the proof plane 
which is used when the apparatus is employed for measuring 
the force of electrostatic attraction and repulsion, 




404 A DICTIONARY OF ELECTRICAL 

In delicate magnetometers, the construction of which differs 
considerably from the form shown in Fig. 275, the deflection 
of the magnet is measured by a beam of light reflected from a 
mirror attached to the axis of suspension. 

Magneto-Optic Rotation.— The rotation of the plane 
of polarization of a beam of light on its passage through a 
transparent medium placed in a strong magnetic field, 
which medium only p6ssesses such properties while in the 
field. 

In a ray of ordinary light the vibrations of the ether parti- 
cles are at right angles to the direction of the ray, or to the 
direction in which the light is moving. Successive ether 
particles that lie along the path of the ray, do not, however, 
perform their vibrations in the same plane. Each successive 
particle moves in a plane which, though at right angles 
to the ray, is slightly inclined to the neighboring particle. 

The motion of the particles therefore, would describe a 
screw-like path through space. Under certain circumstances, 
all the ether particles may be caused to move in planes that 
are parallel to one another. Such a beam of light is called a 
plane polarized beam. 

A plane polarized beam, when passed through many trans- 
parent substances, will have its ether particles vibrating in 
the same plane when it emerges from the medium, as it had 
before it entered. Other substances possess the property of 
rotating or turning the plane of polarization of the light to 
the right or to the left. This property is called respectively 
right-handed rotary polarization, and left-handed rotary 
polarization. 

Many substances that ordinarily possess no power of rotary 
polarization acquire this power when placed in a magnetic 
field. This property of a magnetic field was discovered by 
Faraday. The effect is to be ascribed to the strain produced 
in the transparent medium by the stress of the magnetic field. 
It may be caused in solid bodies by mechanical forc§, 



WORDS, TERMS AND PHRASES. 



405 



The apparatus for demonstrating the rotation of the plane 
of polarization by a magnetic field is shown in Fig. 276. 

A powerful electro-magnet M, N, is provided with a hollow 
core. The substance c, is placed in the field thus produced 
by the approached poles, and its action on the light of a 
lamp, placed opposite at I, is observed by suitable apparatus 
at a. 

Magnetophone. — An apparatus for measuring the num- 
ber of breaks or interruptions of a circuit by the pitch of the 
musical note heard in an electro-magnetic telephone placed in 
such circuit. (See Telephone, Electro-Magnetic.) 




Fig. €76. 

A similar apparatus is useful in studying the distribution of 
the magnetic field of a dynamo electric machine. In this case, 
a small thin coil of insulated wire is held in the different 
regions around the machine, while the telephone is held to the 
ear of the observer. Magnetic leakage, or useless dissipation of 
lines of magnetic force outside the field proper of the machine, 
is at once rendered manifest by the musical note caused by 
variations in the intensity of the field. 

Since the intensity of the note heard will vary according to 



406 



A DICTIONARY OF ELECTRICAL 



the intensity of the field, and also according to the position in 
which the coil is held, such a coil becomes a magnetic explorer, 
and by its use the distribution and varying- intensity of an 
irregular field can be ascertained. Its use is especially advan- 
tageous in proportioning dynamo-electric machines, and elec- 
tric motors. 

Magnetism. — That branch of science which treats of the 
properties of a magnetic field. (See Field, Magnetic.) 

Magnetism, Ampere's Theory of.— A theory or hypo- 
thesis proposed to account for the cause of magnetism by 
the presence of electric currents in the ultimate particles of 
matter. 





Unmagnetize.d 
Fig. 277. 



Magnetized 
Fig. 278. 



This theory assumes . 

(1) That the ultimate particles of all magnetizable bodies 
have closed electric circuits in which electric currents are con- 
tinually flowing. 

(2) That in an unmagnetized body these circuits neutralize 
one another because they have different directions. 

(3) That the act of magnetization consists in such a polariza- 
tion of the particles as will cause these currents to flow in one 
and the same direction, magnetic saturation being reached 
when all the separate currents are parallel to one another. 

(4) That the coercive force is due to the resistance these 
circuits offer to a change in the direction of their planes. 



WORDS, TERMS AND PHRASES. 40*7 

Figs. 277 and 278, show the circular paths of some of these 
circuits. Fig\ 277 shows the assumed condition of an unmag- 
netized bar. Fig-. 278 the assumed condition of a magnetized 
bar. 

A careful inspection of the figures will show that in a magne- 
tized bar all the separate currents flow in the same direction. 
All the circuits except those on the extreme edge of the bar 
will, therefore, have the currents flowing in them in opposite 
directions to that in their neighboring circuits, and, therefore, 
will neutralize one another. There will remain .however, a 
current in a circuit on the outside of the bar, which must 
therefore be regarded as the magnetizing circuit. 

Guided by these considerations, Ampere produced a coil of 
wire, called a solenoid, which is the equivalent of the magnetiz- 
ing circuit assumed by his theory. 

It therefore follows that an electric current sent through a 
coil of insulated wire surrounding a rod or bar of soft iron, or 
other readily magnetizable material, will make the same a 
magnet. A magnet so produced is called an electro-magnet. 
(See Electro-Magnet.) 

The magnetizing coil is called a helix or solenoid. (See 
Solenoid, Electro-Magnet ie.) 

The polarity of the magnet depends on the direction of the 
current, or on the direction of winding of the helix or sole- 
noid. (See Solenoids, Sinistro?*sal and Dextrorsal.) 

Magnetism, Electro Magnetism produced 

be means of electric currents. 

The discovery of Oersted, in 1820, of the action of an elec- 
tric current on a magnetic needle, was almost immediately 
followed by the simultaneous and independent discoveries of 
Arago and Davy, of the method of magnetizing iron by the 
passage of an electric current around it. 

These observations were first reduced to a theory by Am- 
pere. (See Magnetism, Ampere's Theory of. Electro-Mag- 
net.) 



»/ 



408 A DICTIONARY OF ELECTRICAL 

Magnetism, Hughes' Theory of A theory pro- 
pounded by Hughes to account for the phenomena of magnet- 
ism apart from the presence of electric currents. 

Hughes' theory, or, more strictly speaking, hypothesis of 
magnetism, though very similar to that of Ampere, does not 
assume the improbable condition of a constantly flowing- 
electric current. 

Hughes' hypothesis assumes : 

(1) That the molecules of matter, and probably even the 

n s n s n s atoms, possess naturally op- 

n^ ^ 00t "^^s p o s i t e magnetic polarities 

>? 1 which are respectively -f- and 

\« — > or N. and S. 

I J s (2) That these molecules, 

n * in when arranged in closed 

S V y's chains or circuits, are capable 

s^^ ^^ ^ of neutralizing one another so 

n s n s n s n far as external action is con- 

Fig. 279. cerned. 

Two such arrangements or groupings are shown in Figs. 

279 and 280. It will be observed that the magnetic chain 

or circuit is complete, and that, therefore, the substance can 

possess no magnetic properties so far as external action is 

concerned. 

n s n s n s n s n .<? n s n s n s n s n s 

-mi n iiHHfiiifiit 

s n s n s n s n s n s n s n s n s n b n 
Fig. 280. 

(3) That the act of magnetization consists in such a rota- 
tion of the molecules, that a polarization of the substance is 
effected ; that is, the molecules are rotated on their axes so 
that one set of poles tend to point in one direction, and the 
other set of poles in the opposite direction. 



WORDS, TERMS AND PHRASES. 409 

Partial magnetization consists in partial polarization. Mag- 
netic saturation is reached when the polarization is complete. 
(See Magnetic Saturation.) 

Coercive force is the resistance the body offers to the polariza- 
tion or rotation of its molecules. (See Coercive Force.) 

Hughes' hypothesis of magnetism would appear to be 
strengthened by the following facts : 

(1) A bar of steel or iron is sensibly elongated on be- 
ing magnetized. This would naturally result if the mole- 
cules be supposed to be longer in one direction than in any 
other. 

(2) A tube, furnished at its ends with plates of flat glass and 
filled with water containing finely divided magnetic oxide of 
iron, is nearly opaque to light when unmagnetized, but will 
permit some light to pass through it when magnetized. 

(3) A magnet, if cut at its neutral point, will possess op- 
posite polarities at the cut ends ; and no matter to what ex- 
tent tins subdivision is carried the particles will still possess 
opposite polarities. 

These facts are, however, also explained by Ampere's hy- 
pothesis of magnetism, with, however, the improbable as- 
sumption of a constantly flowing current in each molecule. 

Magnetism, Lamellar (See Lamellar Magne- 
tism.) 

Magnetism, Solenoidal Distribution of A 

term sometimes applied to a distribution of magnetism in a bar 
such that the magnetized particles are arranged with their 
poles in the direction of the length of the bar, in contra-dis- 
tinction to a lamellar distribution. (See Lamellar Distribu- 
tion of Magnetism.) 

Magnetization, Coefficient of (See Coefficient 

of Magnetization.) 

Magnetization, Critical Current of (See 

Critical Current of Magnetization.) 



410 A DICTIONARY OF ELECTRICAL 

magnetization, Methods of Magneti- 
zation effected either by induction from another mag-net, or 
by means of induction by an electric current. 

The substance to be magnetized is brought into a magnetic 
field, so that the lines of magnetic force pass through it. All 
methods of magnetization may be divided into methods of 
touch, and magnetization by the electric current. 

Mains, Electric The principal conductors in any 

system of electric distribution. (See Leads, Electric.) 

Mallet, Electro-Magnetic — (See Electro-Mag- 
netic Mallet.) 

Manipulator, Breguet's (See Needle Tele- 
graph.) 

Manometer. — An apparatus for measuring the tension or 
pressure of gases. 

Manometers are either mercurial or metallic. They meas- 
ure the pressure of gases either in atmospheres, i. e., in mul- 
tiples or decimals of 15 pounds to the square inch, or in inches 
of mercury. 

Marine Galvanometer. — (See Galvanometer, Marine.) 
Mariners' Compass. — (See Compass, Azimuth.) 
Marked Pole of a Magnet. — The pole of a magnet 
that points approximately to the geographical north. 

If the pole of the magnet that points to the geographical 
north be in reality the north pole of the magnet, then the 
earth's magnetic pole in the Northern Hemisphere is of south 
magnetic polarity. In the United States, and Europe gener- 
ally, this is regarded to be the fact. 

The French, however, call the pole of the needle that points 
to the earth's geographical north, the south or austral pole. 
In America and England it is called the north pole, the marked 
pole, or the north-seeking pole, and the Northern Hemisphere 
is assumed to possess south magnetic polarity. (See Aus- 
tral and Boreal Poles.) 



WORDS, TERMS AND PHRASES. 411 

Markers. — Green flags, or signal lights, displayed on the 
ends of trains, in systems of block railway signalling in order 
to avoid accidents from trains breaking in two. (See Block 
Signals, System of.) 

Iflass. — The quantity of matter contained in a body. 

Mass must be carefully distinguished from weight. The 
weight of a given quantity of matter depends on the attraction 
which the earth possesses for it, and this, on the earth's sur- 
face, varies with the latitude, being greatest at the poles, and 
least at the equator. It also varies with different elevations 
above the level of the sea. The mass, however, is the same 
under all circumstances. 

mass, Magnetic* Such a quantity of magne- 
tism, that at unit distance produces an action equal to unit 
force. 

Mass, Unit of The quantity of matter which 

under certain conditions will balance the weight of a standard 
gramme or pound. 

Masses, Eleetrie A mathematical conception 

for such quantities of electricity that at unit distance will 
produce an attraction or repulsion equal to unit force. 

Electrical masses are assumed to be equal when they pro- 
duce on two identical bodies of small dimensions charges of 
the same electric force. 

Mast er-lioek. — The central or controlling clock in a sys- 
tem of electric time distribution, from which the time is 
transmitted to the secondary clocks in the circuit. (See 
Clocks, Electric.) 

matter. — That which occupies space and prevents other 
matter from simultaneously occupying the same space. 

Matter is composed of atoms, which unite to form molecules. 
(See Atoms. Molecules.) 

matter, .Elementary (See Element.) 



412 A DICTIONARY OF ELECTRICAL 

Hatter, Radiant, or Ultra-Gaseous A 

term proposed by Crookes for the peculiar condition of the 
matter which constitutes the residual atmospheres of high 
vacua. 

The peculiar properties of radiant matter are seen in the 
mechanical effects of the localized pressure produced when 
such residual atmospheres are locally heated or electrified. 

In Crookes' Radiometer, vanes of mica, silvered on one face 
and covered with lampblack on the opposite face, are sup- 
ported on a vertical axis, so as to be capable of rotation and 
placed in a glass vessel in which a high vacuum is maintained. 
On exposing the instrument to the radiation from a candle or 
gas flame, a rapid rotation takes place. 

The explanation is as follows : The lampblack covered sur- 
faces absorb the radiant heat, and becoming heated the 
molecules of gas in the residual atmosphere are shot violently 
from these heated surfaces, and by their reaction drive the 
vanes around in the opposite direction to that from which 
they are thrown off. The molecules are also shot off from the 
silvered surfaces, but, as these are cooler, the effect is not as 
g'reat as at the blackened surfaces. 

In a gas, at ordinary pressure, the heated surfaces are also 
bombarded by other molecules of the gas, but in high vacua the 
mean free path of the molecules is such that there is no inter- 
ference, a Crookes' layer existing between the vanes and the 
walls of the glass vessel. (See Layer, Crookes\) 

When a Crookes' tube is furnished with suitable electrodes, 
and electric discharges are sent through it between these 
electrodes, a stream of molecules is thrown off in straigr t 
lines from the surface of the negative electrode. 

Some of the effects of this molecular bombardment are seen 
by the use of the apparatus shown in Fig. 281. When the 
positive and negative terminals are arranged as shown, the 
paths of the molecular streams are seen as luminous streams 
whose directions are those shown in the figures. 



WORDS, TERMS AND PHRASES. 



413 



The figure on the left shows the path taken in a low vacuum. 
Streams pass from the negative electrode to each of the pos- 
itive electrodes. 

The figure on the right shows the discharge in a high 
vacuum. Here the streams pass off at right angles to the face 




Fig. 281. 

of the negative electrode, and proceed therefrom in straight 
lines, independently of the position of the positive electrode. 
Since, therefore, the negative electrode at «,' is in the shape of 
a concave mirror, the luminous particles converge to a focus 
near the centre of the glass vessel, and then diverge to the 
opposite wall. 



414 



A DICTIONARY OF ELECTRICAL 



Refractory substances placed at such a focus of molecular 
bombardment, as shown in Fig. 282, are rendered incan- 
descent. 

In a similar manner, phosphorescent substances exposed to 
such molecular streams emit a beautiful phosphorescent light. 
(See Phosphorescence, Electric.) 

Measurements, Electric Determinations of 

the values of the E. M. F., resist- 
ance, current, capacity, energy, 
etc., in any electric circuit. 

Electric measurements may be 
either qualitative or quantitative. 

Mechanical Equivalent of 
Heat. — The amount of mechanical 
energy converted into heat that 
would be required to raise the tem- 
perature of one pound of water 1° F. 

The mechanical equivalence be- 
tween the energy expended and the 
heat produced. 

Joule's experiments, the results of 
which are generally accepted, gave 
772 foot pounds as the energy equiv- 
alent to that expended in raising 
the temperature of one pound of 
water 1° F. 

Media, Anisotropic 

Fig. 282. (See Anisotropic Media.) 
Meg or Mega (as a prefix.) — One million times; as meg- 
ohm, one million ohms ; mega-volt, one million volts. 
Meidinger's Voltaic Cell.— (See Cell, Voltaic.) 
Meridian, Geographic The geopraphic meri- 
dian of a place is a great circle passing through the place and 
the north and south geographic poles of the earth, 




WORDS, TERMS AND PHRASES. 415 

Meridian, Magnetic The great circle passing 

through the poles of a magnetic needle at rest in the earth's 
magnetic field. 

Metallic Arc. — A voltaic arc formed between metallic 
electrodes. (See Arc, Voltaic.) 

Metallic Circuit. — Any circuit that is mainly metallic 
throughout, or of which the ground or earth does not form a 
part. (See Circuit, Metallic.) 

Metallochroines or Nobili's Rings. — Prismatic 
colored deposits obtained by the electrolytic decomposition of 
metallic salts under certain conditions. 

These deposits consists of peroxide of lead which appears 
at the positive electrode. The colors, like those produced by 
soap-bubble films, or by the iridescence of mother-of-pearl, 
or by films of oil floating on the surface of water, etc., are 
due to the interference of the light reflected from the upper 
and lower surfaces of films which are deposited in different 
thicknesses. 

Metalloid. — A name formerly applied to a non-metallic 
body, or to a body having only some of the properties of a 
metal as carbon, boron, oxygen, etc. 

The term is now but little used. 

Metals, Deflagration of The volatilization of 

metals, generally by electric incandescence. 

Metals, Electrical Protection of The pro- 
tection of a metal from corrosion by placing it in connection 
with another metal, which, when exposed to the corroding 
liquid, vapor, or gas will form with the metal to be protected, 
the positive element of a voltaic couple. 

The negative element of a voltaic couple is protected by the 
presence of the positive element, which is alone corroded. 
This method has been adopted with considerable success to 



416 A DICTIONARY OF ELECTRICAL 

electrically protect metals from corrosion. A few examples 
will suffice. (See Cell, Voltaic.) 

(1) Davy proposed to protect the copper sheathing of ships 
from corrosion by attaching- pieces of zinc to the copper 
sheathing-. This succeeded too well since the copper salts 
which were formerly produced and acted as a poison to the 
marine plants and animals, being now absent, permitted these 
forms of life to thrive to such an extent as to seriously foul 
the ship's bottom. 

(2) A ring of zinc attached to a lightning rod, near its points 
has, it is claimed, the power of protecting the points from cor- 
rosion. 

(3) Iron bars of railings, if sunk or embedded in zinc, are pre- 
served from corrosion near the junction of the two metals, 
but if sunk in lead are rapidly corroded, because iron is elec- 
tro-positive to lead, but electro-negative to zinc. 

(4) Tinned iron rapidly corrodes or rusts when the iron is ex- 
posed to the atmosphere by a scratch or abrasion, because the 
iron is electro-positive to tin. Nickel-plated iron, for the 
same reason, rusts rapidly on the exposure of an abraded sur- 
face. 

(5) Zinced or galvanized iron, or iron covered with a deposit 
of zinc, is protected from corrosion because the zinc, being 
positive to iron, can alone be corroded, and the zinc is pro- 
tected in part by the coating of insoluble oxide formed. 

Meter, Current (See Galvanometer.) 

Meters, Electric Apparatus for measuring 

commercially, the quantity of electricity that passes in a 
given time, through any consumption circuit. 

Electric meters are constructed of a great variety of forms ; 
they may, however, be arranged under the following heads : 

(1) Electro-Magnetic Meters, or those in which the current 
passing is measured by the electro-magnetic effects it pro- 
duces, 



WORDS, TERMS AND PHRASES. 417 

In such meters the entire current may pass through the 
meter. 

(2) Electro- Chemical Meters, or those in which the current 
passing is measured by the electrolytic decomposition it 
effects. 

In these meters, a shunted portion only of the current is 
usually passed through a solution of a metallic salt, and the 
current strength determined by the amount of electrolytic 
decomposition thus effected. 

(3) Electro-Thermal Meters, or those in which the current 
passing is measured by a movement effected by the increase 
in temperature of a resistance through which the current 
is passed, or by the amount of a liquid evaporated by the heat 
generated by the current. 

(4) Electric-Time Meters, or those in which no attempt is 
made to measure the current that passes, but in which a 
record is kept of the number of hours that an electric lamp, 
motor, or other electro-receptive device, is supplied with the 
current. 

Edison's electric meter is of the second class. It consists of 
two voltameters, or electrolytic cells, containing zinc sulphate, 
in which two plates of chemically pure zinc are dipped. The 
current that passes is determined by the amount of the varia- 
tion in weight of the zinc plates. To determine this, the plates 
are weighed at stated intervals : one plate every month, the 
other plate, which is intended to act as a check on the first, only 
once in three months. Some difficulty has been experienced 
in meters of this class, from the variations in the value of the 
shunt resistance, due to variations in the condition and tem- 
perature of the electrolytic cell. The use of a compensating 
resistance, however, has, it is claimed, removed this objec- 
tion. 

Methods of Magnetization by Touch.— 

These are three, viz.: 

(1) Single Touch. A Method for effecting the magnetiza- 



418 A DICTIONARY OF ELECTRICAL 

tion of a bar or other magnetizable material by touch from 
a single magnet. 
In single touch the magnetizing mag-net is simply drawn 
over the bar to be magnetized from end 
to end and returned through the air, the 
stroke being repeated a number of times. 
The end of the pole the magnet leaves 
is thus magnetized oppositely to that of 
the magnetizing pole. 

By some writers the method of single 

ppN s | touch is described as that effected by 

■* — placing the magnetizing - magnet N S, 

Fig. 283. Fig. 283, on the middle of the bar to be 

magnetized and drawing it to the end and returning through 
the air as before, and then reversing the pole, placing it on 
the middle of the bar, and drawing it towards the other end. 
The former would, however, appear to be the better use of the 
term single touch. 




Fig. 28h. 

(2) Separate Touch. 

In separate touch two magnetizing bars are placed with 
their opposite poles at the middle of the bar to be magnetized 
and drawn away from each other towards its ends, as shown 




Fig. 285. 

in Fig. 284. This motion is repeated a numb er of times, the 
poles being returned through the air. 
In the above, as in all cases of magnetization by touch, 



WORDS, TERMS AND PHRASES. 



419 



better effects are produced if the bar to be magnetized is rested 
on the opposite poles of another magnet, or placed near them, 
as shown in Fig. 285. 

(3) Double Touch. 

In double touch the two magnets are placed with their 
opposite poles together on the middle of the bar to be magnet- 
ized, as shown in Fig. 285. They are then moved to one end of 
the bar, ivhen, instead of removing them and passing them 
back through the air to the other end, they are moved in this 
direction over the bar to be magnetized to the other end, 
and this motion is repeated a number of times. The motion is 
stopped at the middle of the bar, when the magnetizing mag- 
nets are moving in the 
opposite direction to 
that at which they be- 
gan to move. This 
assures an equal num- 
ber of strokes to the 
two halves of the bar. 
The method of double 
touch produces 
stronger magnetiza- 
tion than either of the other methods but does not effect such 
an even distribution of the magnetism, and therefore is not 
applicable to the magnetization of needles. 

A variety of double touch is shown in Fig. 286, where four 
bars to be magnetized are placed in the form of a hollow 
rectangle, with only their ends touching at their edges, the 
angular spaces at the corners being filled with pieces of soft 
iron. The horseshoe magnet N S, is then moved around the 
circuit several times in the same direction. This is believed to 
produce a more uniform magnetization than the ordinary 
method of double touch. 

Methven's Standard Screen.— An upright rectangular 
plate of metal, furnished with a vertical slot of such dimen- 




Fig. 286. 



420 A DICTIONARY OF ELECTRICAL 

sions as will permit an Argand burner, the flame of which is 
three inches high, to send through the slot a light equal to 
two standard candles. 

Metre Bridge. — A slide form of Wheatstone's electric 
balance, in which the slide wire is one metre in length. (See 
Balance, Wheatstone's Slide Form of.) 

Metre Candle. (See Candle, Metre.) 

Metric System of Weights and Measures.— A sys- 
tem of weights and measures adopted by the French, and by 
the scientific world generally. 

For measures of length, the one ten-millionth part of the 
quadrant of a meridian of the earth is taken as the unit of 
length. This unit of length is called a metr^, and various 
subdivisions and multiples of its length are made on the 
decimal system. 

For a system of weights, the weight of one cubic centimetre 
of pure water at 39.2° F., the temperature of the maximum 
density of water, is taken as the unit of weight. This is called 
a gramme, and various multiples, and subdivisions of this 
unit are made on the decimal system. 

The following table of French measures and their corres- 
ponding English values are taken from Deschanel's "Element- 
ary Treatise on Natural Philosophy " : 
Length. 

1 millimetre = .03937 inch, or about ^ inch. 

1 centimetre = .3937 inch. 

1 decimetre = 3.937 inches. 

1 metre = 39.3707 inches = 3.281 ft. = 1.0936 yd. 

1 kilometre = 1093.6 yds., or about f mile. 

More accurately, 1 metre = 39.370432 in. = 3.2808693 ft. = 
1.09362311 yd. 

Area. 

1 sq. millimetre = .00155 sq. inch. 



WORDS, TERMS AND PHRASES. 421 

1 sq. centimetre = .155 sq. inch. 

1 sq. decimetre = 15.5 sq. inches. 

1 sq. metre = 1550 sq. inches = 10.764 sq. ft. = 1.196 sq. yd. 
Volume. 

1 cub. millimetre = .000C61 cub. inch. 

1 cub. centimetre = .061025 cub. inch. 

1 decimetre = 61.0254 cub. inches. 

Cubic metre= 61025 cub. in. = 35.3156 cub. ft. = 1.308 cub. yd. 

The litre (used for liquids) is the same as the cubic deci- 
metre, and is equal to 1.7617 pint, or .22021 gallon. 
Mass and Weight. 

1 milligramme = .01543 grain. 

1 gramme = 15.432 grains. 

1 kilogramme = 15432.3 grains = 2.205 lbs. avoir. 

More accurately, the kilogramme is 2.20462125 lbs. 
Miscellaneous. 

1 gramme per sq. centimetre = 2.0481 lbs. per sq. ft. 

1 kilogramme per sq. centim. = 14.223 lbs. per sq. in. 

1 kilogrammetre = 7.2331 foot-pounds. 

1 force cle clieval = 75 kilogram metres per second, or 542^ 
foot-pounds per second, nearly, whereas 1 horse-power (Eng- 
lish) = 550 foot-pounds per second. 

Conversion of English into French measures : 
Length. 
1 inch = 2.54 centimetres, nearly. 
1 foot = 30.48 centimetres, nearly. 
1 yard = 91.44 centimetres, nearly. 
1 statute mile = 160933 centimetres, nearly. 
More accurately, 1 inch = 2.5399772 centimetres. 

Area. 
1 sq. inch = 6.45 sq. cm., nearly. 
1 sq. foot = 929 sq. cm., nearly. 
1 sq. yard = 8361 sq. cm., nearly. 
1 sq. mile = 2.59 x 10 10 sq. cm., nearly. 



422 A DICTIONARY OF ELECTRICAL 

Volume. 
1 cub. inch = 16.39 cub. cm., nearly. 
1 cub. foot = 28316 cub. cm., nearly. 
1 cub. yard = 764535 cub. cm., nearly. 
1 gallon = 4541 cub. cm., nearly. 

Mass. 
1 grain = .0648 gramme, nearly. 
1 oz. avoir. = 28.35 gramme, nearly. 
1 lb. avoir. = 453.6 gramme, nearly. 
1 ton = 1.016 x 10 6 gramme, nearly. 
More accurately, 1 lb. avoir. = 453.59265 gm. 

Velocity. 
1 mile per hour = 44.704 cm. per sec. 
1 kilometre per hour = 27.7 cm. per sec. 



Density. 
1 lb. per cub. foot = .016019 gm. per cub. 
62.4 lbs. per cub. ft. = 1 gm. per cub. cm. 



cm. 



Force (assuming g = 981). 
Weight of 1 grain = 63.57 dynes, nearly. 

1 oz. avoir. = 2.78 x 10 4 dynes, nearly. 

1 lb. avoir. = 4.45 x 10 5 dynes, nearly. 

1 ton = 9.97 x 10 8 dynes, nearly. 

1 gramme = 981 dynes, nearly. 

1 kilogramme = 9.81 x 10 5 dynes, nearly. 

Work (assuming g = 981). 
1 foot-pound = 1.356 x 10 7 ergs, nearly. 
1 kilogrammetre = 9.81 xlO 7 ergs, nearly. 
Work in a second by one theoretical " horse power" = 7.46 
x 10° ergs, nearly. 

Stress (assuming g = 981). 
1 lb. per sq. ft. = 479 dynes per sq. cm., nearly. 
1 lb. per sq. inch = 6.9 x 10 4 dynes per cm., nearly. 
1 kilog. per sq. cm. = 9.81 x 10 5 dynes per sq. cm., nearly. 



Words, terms and phrases. 423 

760 mm. of mercury at 0° C. = 1.014 x 10 6 dynes per sq. cm., 
nearly. 

30 inches of mercury at 0° C. = 1.163 X 10 6 dynes per sq. 
cm., nearly. (DeschaneVs Natural Philosophy.) 

Hlho. — A term proposed by Sir Wm. Thomson for the 
practical unit of conductivity. 

A mho is such a unit of conductivity as is equal to the re- 
ciprocal of one ohm. 

1 

The conducting" power is equal to — or the reciprocal of the 

R 
resistance. 

The word mho, as is evident, is obtained by inverting the 
order of sequence of the letters in the word ohm. 

Micro (as a prefix). — The one millionth ; as, a microfarad, 
the millionth of a farad ; a microvolt, the one millionth of a 
volt. 

Micrometer, Arc An apparatus for the accurate 

measurement of the length of a voltaic arc by means of a 
micrometer. 

The distance between two carbon electrodes — one mova- 
ble and the other fixed — placed inside a glass vessel, is accu- 
rately determined by means of a micrometer placed on the 
movable electrode. The operation is similar to that of the 
vernier wire-gauge. (See Wire-Gauge, Vernier.) 

Microphone. — An apparatus invented by Prof. Hughes 
for rendering faint or distant sounds distinctly audible. 

The microphone depends for its operation on variations 
produced in the resistance of the circuit of a small battery and 
receiving telephone by means of a loose contact. 

The loose contact may take a variety of forms. Originally, 
it was made in the form shown in Fig. 287, in which a small 
piece of carbon E, pointed at both ends, is inserted in holes 
near the ends of cross pieces of carbon B and C. The thin 



424 



A DICTIONARY OF ELECTRICAL 



upright board A, on which these are supported, acts as a 
sounding- board or diaphragm, and its movements by sound 
waves is at once audible to a person listening at the receiving 
telephone. The walking of a fly over the sounding board is 
heard as a very much louder sound. 

The forms of transmitting telephone invented by Reis, 
Edison, Blake, Berliner and others, are in reality varieties of 
microphones. 




Fig. 287. 

Microphone Relay. — A device for automatically repeat- 
ing a telephone message over another wire. 

A form of microphone relay is shown in Fig. 288. 

Several minute microphones, mounted on the diaphragm of 
the telephone whose message is to be repeated, so vary the 
resistance of a local battery included in their circuit as to 
automatically repeat the articulate speech received. 

The microphones may be connected either in multiple-arc 
or in series, as shown in Fig. 289. 

Microtasimeter. — An apparatus invented by Edison to 



WORDS, TERMS AND PHRASES. 



425 



measure minute differences of temperature, or of moisture, by 
the resulting differences of pressure. 

A change of temperature, or moisture, is caused to produce 
variations in the resistance of a button of compressed lamp- 
black, placed in the circuit of a delicate galvanometer. The 




Fig. 288. 

apparatus, though of surprising delicacy, is scarcely capable 
of practical application, from the fact that the resistance of 
the carbon does not resume its normal value on the removal 
of the pressure. 

Mil. — A unit of length used 
in measuring the diameter of 
wires, equal to the t Jqtt of an 
inch, or .001 inch. 



Mil, Circular 



-A 





unit of area employed in meas- Fig. 289. 

uring the areas of cross sections of wires, equal to .78540 square 

mil. 

One circular mil = .78540 square mil. 

The area of cross section of a circular wire one mil in di- 
ameter is equal to .78540 square mil. (See Circular Units, etc.) 



426 A DICTIONARY OF ELECTRICAL 

Mil, Square A unit of area employed in measur- 
ing the areas of cross sections of wires, equal to .000001 square 
inch. 

One square mil = 1.2732 circular mil. 

M ill i (as a prefix). — The one-thousandth part. 

IVIilli- Ampere.— The thousandth of an ampere. 

Milli-Oerstedt. — The one-thousandth of an Oersted! 

Mimosa Sensitiva, or Sensitive Plant. — A sensitive 
plant whose leaves fold or shut up when touched. 

The fibres of all the sensitive plants, such for example as the 
above, the Venus' fly-trap, ete., like all muscular fibre, and 
indeed all protoplasm, suffer contraction when traversed by 
electric currents. 

Pouillet concludes from numerous observations that the free 
positive electricity of the atmosphere is partly due to the vapors 
disengaged by growing plants. 

The peculiar geographical distribution of thunder storms, 
however, does not favor this assumption. 

Mine Exploder, Electro-Magnetic (See Ex- 
ploder, Electric. Fuse, Electric.) 

Miophone. — An application, by Boudet, of the micro- 
phone for the medical examination of the muscles. 

Mirror Galvanometer,— (See Galvanometer, Mirror.) 

Moisture, Effect of on Electrical Phe- 
nomena. — The presence of moisture on the surfaces of in- 
sulators permits the loss or dissipation of an electric charge. 
This loss is more rapid with negatively charged bodies than 
with those positively charged. 
Molar, or Mass Attraction. — (See Gravitation.) 
Molecular Attraction. — (See Attraction, Molecular.) 
Molecular Bombardment.— (See Matter, Radiant or 
Ultra- Gaseous.) 



WORDS, TERMS AND PHRASES. 427 

molecular Chain. — A polarized chain of molecules that 
exists in an electrolyte during its electric decompcsition, or in 
a voltaic cell on closing its circuit. (See Grothuss' Hypothesis.) 

molecular Heat.— (See Heat, Molecular.) 

Molecular Rigidity, or Coercive Force.— (See 
Coercive Force.) 

molecule, Gramme The weight of any substance 

taken in grammes numerically equal to the molecular weight. 

The gramme molecule represents the number of small cal- 
ories of heat required to raise one gramme of the substance 
through 1° C. (See Calorie.) 

moment of Couples. — (See Couples, Moment of .) 

moment, magnetic (See Magnetic Moment.) 

Honophotal Arc Light Regulator.— A term some- 
times employed to distinguish an arc electric lamp in which 
the whole current passes through the arc regulating mechan- 
ism, and which is usually operated singly in circuit with a 
dynamo. Maier. (See Polyphotal.) 

morse Alphabet. — (See Alphabet, Morse.) 

morse Recorder, or Register. — (See Recorder, 
Morse's.) 

morse System of Telegraphy. — (See Telegraphy, 
Morse.) 

morse's Telegraphic Sounder. — (See Sounder, 
Morse's Telegraphic.) 

motograph, Electro — An apparatus for the 

electric transmission of signals, in which the receiving instru- 
ment is operated by the slipping of a lever over a cylinder 
of moistened chalk, on the passage of the current. (See Elec- 
tro Motograph.) 

The solution for moistening the paper consists of sodium 
chloride and pyrogallic acid dissolved in water. 

motor, Electric — A device for transforming 

electric power into mechanical power. 



428 A DICTIONARY OF ELECTRICAL 

All practical electric motors depend for their operation on 
magnetic attraction or repulsion. The entire magnetism 
may be produced by the current, or part may be obtained 
from permanent magnets, and the rest from electro mag- 
nets. 

A dynamo electric machine will act as a motor if a current 
is sent through it. Such a motor is sometimes called an 
electro motor. The term electric motor would, however, ap- 
pear to be the preferable one. 

In all cases the rotation is in such a direction as to induce in 
the armature an electromotive force opposed to that of the 
driving current, this is therefore called the counter electro- 
motive force. 

A Magneto Dynamo, or a dynamo the field of which is 
obtained from permanent magnets, or a Separately Excited 
Dynamo, will operate as a motor when a current is sent 
through its armature, and will turn it in the opposite direction 
to that required to drive it in order to produce current. 

A Series Dynamo, will operate as a motor when a current is 
sent through it. If the current is sent through it in the opposite 
direction to that which it produces when in operation as a gener- 
ator, the polarity of the field is reversed and the dynamo will 
turn as a motor in the opposite direction to that required to 
produce the current. If the current is reversed the polarity 
of both the field and the armature is again reversed, and the 
dynamo still rotates as a motor in the opposite direction to 
that in which it is rotated as a generator. 

A series dynamo, therefore, always rotates as a motor in a 
direction opposite to that of its rotation as a generator. 

When, however, the polarity of the field only is reversed by 
changing the connection between the armature and the field, 
the rotation is in the same direction. 

A Shunt Dynamo operated as a motor will also turn in but 
one direction, but this direction is the same as that in which 
it turns when operating as a generator; for, if the direction 



WORDS, TERMS AND PHRASES. 429 

of ttie current in the armature is the same as in a generator, 
that in the shunt is reversed. 

A Compound-Wound Dynamo will move in a direction 
opposite to that of its motion as a generator if the series part 
is more powerful than the shunt, and in the same direction if 
the shunt part is more powerful than the series. To use a 
compound-wound dynamo as a motor it is necessary merely 
to reverse the connections of the series coils. 

Alternating- Current Dynamo. — The current from an alter- 
nating-current dynamo, if sent through a similar alternating- 
current dynamo running at the same speed, will drive it as a 
motor. Such a machine possesses the disadvantage of requir- 
ing to be maintained at a speed depending on that of the 
driving dynamo, and also that it requires to be brought to 
this speed before the driving current is supplied to it. As a 
result of this last requirement, variations in the load are apt 
to stop the motor. Considerable improvements, however, are 
being introduced into alternate-current motors, by which these 
difficulties are almost entirely removed. 

An alternating current sent through any self-exciting 
dynamo-electric machine, such as a shunt or series machine, 
will drive it continuously as a motor. The sudden reversals 
in the magnetization of its cores will, however, unless they 
are thoroughly laminated, set up powerful eddy currents that 
will injuriously heat the machine. 

The Reversibility of any Dynamo-Electric Machine, or its 
ability to operate as a motor if supplied with a current, leads 
to a fact of great importance in the efficiency of electric 
motors. This fact is that during the rotation of the armature 
there is induced in it, during its passage through the field of 
the machine, an electromotive force opposed to that produced 
in the armature by the driving current, or a counter-electro- 
motive force. (See Spurious Resistance. Counter Electro- 
motive Force.) This counter electro-motive force acts as a 
spurious resistance, and opposes the passage of the driving 



430 A DICTIONARY OF ELECTRICAL 

current, so that, as the speed of the electric motor increases, 
the strength of the driving current becomes less, until, when 
a certain maximum speed is reached, no current passes. In 
actual practice, this maximum speed is not attained, or is 
only momentarily attained, and a small, nearly constant, cur- 
rent is expended in overcoming friction at the bearings, air 
friction, etc. 

When, however, the load is placed on the motor, that is, 
when it is caused to do work, the speed is reduced and the 
counter electromotive force is decreased, thus permitting a 
greater current to pass. The fact that the load thus auto- 
matically regulates the current required to drive the motor, 
renders electric motors very economical in operation. 

The relations, between the power required to drive the 
generating dynamo, and that produced by the electric motor, 
are such that the maximum work per second is done by the 
motor, when it runs at such a rate that the counter electro- 
motive force it produces is half that of the current supplied to 
it. The maximum work or activity of an electric motor is 
therefore done when its theoretical efficiency is only 50 per 
cent. This, however, must be carefully distinguished from 
the maximum efficiency of an electric motor. A maximum 
efficiency of 100 per cent, can be attained theoretically, and, in 
actual practice, considerably over 90 per cent, is obtained. In 
such cases, however, the motor is doing work at less than its 
maximum power. 

An efficiency of 100 per cent, is reached when the counter 
electromotive force of the motor is equal to that of the source 
supplying the driving current. Supposing now the driving 
machine to be of the same type as the motor, the two 
machines are now running at the same speed. If now a load 
is put on the motor so as to reduce its speed, and thus permit 
it to produce a counter electromotive f Ox'ce of but 90 per cent. , 
its efficiency will be but 90 per cent. In such a case, therefore, 
the efficiency is represented by the relative speeds of the gener- 
ator and the motor. 



"WORDS, TERMS AND PHRASES. 431 

motor Electromotive Force.— A term proposed by 
F. J. Sprague for the counter electromotive force of an electric 
motor. (See Counter Electromotive Force.) 

This term was proposed by Sprague as expressing the 
necessity for the existence of a counter electromotive force in 
an electric motor, in order to permit it to utilize the energy 
of the electric current which drives it. 

Motor, Pjro-Magnetic — (See Pyro-Magnetic 

Motor.) 

Mouse-Mill. — A form of convection induction machine 
invented by Sir Wm. Thomson to act as the replenisher of his 
Electrometer. (See Electrostatic Induction Machines. Re- 
plenisher.) 

Mouse-Mill Dynamo, Sir Wm. Thomson's 

A dynamo electric machine designed by Sir 

Wm. Thomson, named from the resemblance of its armature 
to a mouse mill. 

The armature conductor of this dynamo consists of parallel 
bars of copper, arranged on a hollow cylinder like the bars on 
a mouse-mill. 

Mouth Pieces.— Openings into air-chambers, generally 
circular in shape, placed over the diaphragms of telephones, 
phonographs, gramophones, or graphophones to permit the 
application of the voice in speaking so as to set the diaphragm 
into vibration. 

The mouthpiece may also be utilized by the ear of an 
observer listening so as to be affected by its vibrations. 

Mover, Prime In a system of distribution of 

power the motor by which the others or secondary movers are 
driven. 

In a steam plant the steam engine is the prime mover; the 
shafts or machines driven by the main shafts are sometimes 
called the secondary movers. The main shaft is called the 



432 A DICTIONARY OF ELECTRICAL 

driving shaft. Its motion is carried by means of belts to 
other shafts called driven shafts. The belt passes over 
pulleys on the driving and driven shafts. They are called re- 
spectively the driving and driven putties. 
Multiple- Arc Circuit.— (See Circuits, Varieties of.) 
Multiple-Series, Circuit.— (See Circuits, Varieties of.) 
Multiple Switch Board.— (See Board, Multiple Switch.) 

Multiplex Telegraphy.— A system of telegraphy in 
which more than four messages can be simultaneously trans- 
mitted over a single wire, either all in the same direction, or 
part in one direction, and the remainder in the opposite direc- 
tion. (See Telegraphy, Multiplex.) 

Multiplier, Schweigger's (See Galvanometer.) 

Mutual Induction.— (See Induction, Mutual.) 

Muscles, Electrical Excitation of (See Elec- 

trotonus.) 

Muscular Pile, Matteucci's A voltaic battery or 

pile, the elements of which are formed of longitudinal and 
transverse sections of muscle, alternately connected. 

Matteucci's experiments appear to show that the lower the 
animal is in the scale of creation, the stronger is the current 
produced, and the longer its duration. Du Bois-Reymond has 
shown that the muscular current is not clue to contact, but to 
the differences of electric potential naturally possessed by the 
muscles themselves. 

The nerves also possess the power of producing differences 
of electromotive forces and hence currents. (See Electro- 
tonus.) 

Musket, Electric A gun in which the charge is 

ignited by the incandescence of a platinum wire by the action 
of a battery placed in the body of the gun. 

Myria (as a prefix). — A million times. 



WORDS, TERMS AND PHRASES. 433 

Nascent State. — A term used in chemistry to express 
the state or condition of an elementary atom or radical just 
liberated from chemical combination, when it possesses chem- 
ical affinities or attractions more energetic than afterwards. 

According to Grothiiss' hypothesis, during the decomposi- 
tion of a chain of polarized molecules, such for example as that 
of hydrogen sulphate, H 2 S0 4 , in a zinc-copper voltaic cell the 
two atoms of hydrogen H 2 , liberated by the combination of the 
S0 4 , with an atom of zinc Zn, possess a stronger affinity for the 
S0 4 of the molecule next to it, than does its own H 2 , and thus 
liberates its two atoms of hydrogen, which in turn unite with 
the S0 4 , of the next molecule in the polarized chain, and this 
continues until the two atoms of hydrogen liberated from the 
last molecule in the chain are given off at the surface of the 
copper plate. (See Grothiiss 1 Hypothesis.) 

The nascent state of elements is doubtless due to the fact 
that the elements are then in a free state, with their bonds 
open or unsatisfied, and therefore possess greater affinities 
than when they are united in molecules. Thus H — , H — , or 
atomic hydrogen, should possess different affinities than H — H, 
or molecular hydrogen. 

Natural Currents. — (See Earth Currents.) 

Natural Law.— (See Law, Natural.) 

Natural Magnet. — (See Lodestone. Natural Magnet.) 

Needle, Astatic A system of two horizontal 

magnetic needles, with the opposite poles facing each other, 
rigidly attached to a vertical support, on which they are free 
to turn. (See Astatic Needle.) 

The use of an astatic needle lessens the force required to 
deflect the needle either in the earth's field, or in the field 
of another magnet. An astatic needle is shown in Fig. 290. 

Needle, Dipping — A magnetic needle, sus- 
pended so as to be free to move in a vertical plane, employed 
to determine the deviation of the needle from a horizontal 



434 



A DICTIONARY OF ELECTRICAL 



position, or the angle of dip, or magnetic inclination of a 
place. (See Dip, Magnetic. Inclination, Magnetic. Incli- 
nometer. Inclination Chart.) 



Needle, Magnetic 



-(See Compass, Azimuth.) 



Needle of Oscillation. — A small magnetic needle em- 
ployed for measuring the intensity of a magnetic field by 
counting the number of oscillations the needle makes in a given 
time, when disturbed from its position of rest in such field. 
(See Intensity of Magnetization. Isodynamic Lines.) 

Needle, Telegraphic A needle employed in 

telegraphy, the movements of which to the left or right 
respectively, represent the dots and dashes of the Morse 
alphabet. (See Telegraphy, Needle System.) 

Negative Electricity. — One of the 

phases or states of electric excitement. 
An electrically charged body, no 
matter from what source it has received 
its charge, manifests either a negative 
or a positive charge. 

According to the Double Fluid Hy- 
pothesis, each of these phases, or 
varieties of electric excitement, is 
Fig. 290. caused by the presence of a distinct 

and separate fluid, endowed with characteristic properties. 
According to the Single Fluid Hypothesis, negative elec- 
tricity is caused by the deficit of a single fluid, and positive elec- 
tricity by a surplusage of the same fluid. 

According to another view, negative electricity is caused by 
an excess of the universal ether, and positive electricity by its 
deficit. (See Hypotheses of Electricity.) 

Negative Element or Plate, of a Voltaic Cell.— 

That element or plate of a voltaic cell into which the current 
passes from the exciting liquid of the cell. 




WORDS, TERMS AND PHRASES. 



435 



The plate that is not acted on by the electrolyte during the 
generation of current by the cell. The copper, or carbon plate 
respectively in a zinc-copper, or zinc-carbon couple. 

It must be carefully borne in mind that the conductor at- 
tached to the negative element of a voltaic pile, is the positive 
conductor or electrode of the pile, since the current that flows 
into the plate from the liquid or electrolyte, must flow out of 
the plate where it projects beyond the liquid. — (See Cell, Vol- 
taic, Polarity of.) 



Nerve Fibre, Electric Excitability of 

Excitability, Electric, of Nerve Fibre.) 



Nerves, Action of Electricity on 

trot onus. Galvanization. 
Fardization. Galvano- 
Faradization.) 

Net, Faraday's 

— An insulated net of cot- 
ton gauze, or other similar 
material, capable of being 
turned inside out, without 
being thereby discharged, 
employed for demonstrat- 
ing that in a charged, insu- 
lated conductor, the entire 
charge is accumulated on 



—(See 



-(See Elec- 




Fig. 291. 

of the conductor. 



the outside 

Faraday's net, as shown in Fig. 291, consists of a bag N, of 
cotton gauze, or mosquito netting, supported on an insulating 
stand I. When tested by a proof plane, no free electric charge 
is found on the inside, though such a charge is readily detected 
by the same means on the outside. By means of the silk 
strings S, S, the bag can be turned inside out, when the charge 
will then all be found on the then inside or now outside. 

Faraday was in the habit of protecting his delicate electro- 
scopes against outside electrification by covering them with 



436 A DICTIONARY OF ELECTRICAL 

gauze. To properly act as an electric screen, the gauze should 
be connected with the earth. 

Faraday constructed a small insulated room, twelve feet in 
height, breadth, and depth, covered inside with tin-foil, and. 
on charging this room from the outside, he was unable to de • 
tect the presence of the charge, even by the aid of his most 
delicate instruments. This room is often called Faraday's 
Cube. 

Network of Currents.— A term sometimes applied to a 
number of shunt or derived circuits. (See Shunt or Derived 
Circuits. Kirchojfs Law.) 

Neutral Line of Commutator Cylinder.— (See Line, 
Neutral, of Commutator Cylinder.) 

Neutral Points of a Dynamo Electric Machine, 

— Two points of greatest difference of potential, on the com- 
mutator cylinder, situated at the opposite ends of a diameter 
thereof, at which the collecting brushes must rest in order to 
carry off the current quietly. 

These are called the neutral points because the coils that 
are short circuited by the brushes lie in the magnetically neu- 
tral points of the armature. (See Line, Neutral, of Commuta- 
tor Cylinder.) 

Neutral Points of Thermo-Electric IMagram.— 
The points on a thermo-electric diagram where the lines rep- 
resenting the thermo-electric powers of any two metals cross 
each other. 

A mean temperature for any two metals in a thermo-electric 
series, at which, if their two junctions are slightly over and 
slightly under the mean temperature (the one as much above as 
the other is below), no differences of electromotive force are de- 
veloped. (See Diagram, Thermo-Electric. Couple, Thermo- 
Electric.) 

Neutral Points on a Magnet.— Points approximately 
midway between the poles of a magnet. (See Line, Neutral, 
of Magnet. Equator of Magnet.) 



WORDS, TERMS AND PHRASES. 487 

Nickel 15a 111. — (See Baths, Nickel, etc.) 

Ron-Conductors. Insulators. — Substances that offer 
considerable resistance to the passage of an electric current 
through their mass. 

There are no substances known that absolutely prevent the 
flow of an electric current, the difference of potential of which 
is sufficiently great. (See Conductors, Table of.) 

Notation, Algebraic A system of arbitrary 

symbols employed in algebra. 

The following brief description of the notation employed in 
algebra is for the use of the non-mathematical reader: 

Quantities are represented in algebra by letters, such as a 
and b, x, and y, etc. 

Addition is represented thus, a -\- b. 

Subtraction is represented thus, a — b. 

Multiplication is represented thus, axb, or simply by writ- 
ing the letters next to each other ab. 

a 
Division is represented thus, a + b, or — . 

6 

An Exponent, or figure placed to the right of a letter, above 
it as a 3 , indicates that the quantity represented by a, is to 
be multiplied by itself three times, as a x a x a, or a a a. 

A Coefficient, or figure placed to the left of a quantity, in- 
dicates the number of times that quantity is to be taken; thus, 
3 a, indicates that a is to be added three times, thus a -f- a -f- 
a, or 3 X «• 

A Radical Sign or Root, thus <*/ a, or 2 1/ a, indicates that the 
square root of the quantity a, is to be taken. In the same 
manner 3 4/ a, indicates that the cube root of a is be taken. 

1 jl 

These expressions are sometimes written a Y , or a 3 . 

Equality is indicated thus : a 3 = a x a x a, or a- = \/a. 



4S8 A DICTIONARY OF ELECTRICAL 

1 

A negative exponent cr° indicates — , or is the exponent of 

a 2 
the reciprocal of the quantity indicated. 

Null or Zero Methods.— Methods employed in electrical 
measurements, in which the values of the electromotive 
force in volts, the resistance in ohms, or the current in amperes, 
or other similar units, are determined by balancing them 
against equal values of the same units, and ascertaining such 
equalitjr, notb y the deflections of the needle of a galvanometer, 
or of an electrometer, but by the absence of such deflections. 

The advantage of zero-methods is found in the fact that the 
galvanometer or electrometer may then be made as sensitive 
as possible, which is not always the case, since great deflec- 
tions are generally to be avoided, especially in tangent gal- 
vanometers. — (See Galvanometers. Electrometers.) 

Number, Diacritical (See Diacritical Number.) 

Observatory, Magnetic An observatory in 

which observations of the variations in the direction and in- 
tensity of the earth's magnetic field are made. 

Magnetic observatories are generally furnished with self- 
registering magnetic apparatus such as magnetographs, mag- 
netometers, inclinometers. (See Magnetometer. Magneto- 
graph. Inclinometer.) 

Magnetic observatories are generally constructed entirely 
of non-magnetic materials, that is, of such materials as are 
destitute of paramagnetic properties. 

Occlusion of Oases. — The absorption or shutting up of 
a gas in the pores, or on the surfaces of various substances. 

Carbon possesses in a marked degree the property of occlud- 
ing or absorbing gases in its pores. These occluded gases 
must be driven out from the carbon conductor employed in 
an incandescent lamp, since otherwise their expulsion, on 
the incandescence of the carbon consequent on the lighting 



WORDS, TERMS AND PHRASES. 439 

of the lamp, will destroy the high vacuum of the lamp cham- 
ber, and thus lead to the ultimate destruction of the lamp. 
(See Lamp, Electric Incandescent.) 

Odorscope. — An apparatus in which the determination of 
an odor was attempted by the measurement of the effect the 
odorous vapor, or effluvia, produced on a variable contact re- 
sistance. 

The microtasimeter was used in connection with the odor- 
scope. (See Diagometer. Microtasimeter.) 

Oerstedt, An A proposed term for the unit of 

electric current, in place of an ampere. 

The term has not been adopted. 

Oil in — The unit of electric resistance. 

Such a resistance as would limit the flow of electricity under 
an electro-motive force of one volt to a current of one ampere, 
or to one coulomb per second. (See B.A. Unit. Legal Ohm. 
Standard Ohm.) 

Ohm, Legal (See Legal Ohm) 

Ohmic or True Resistance. — The time resistance of a 
conductor due to its dimensions, and specific conducting 
power, as distinguished from the spurious resistance produced 
by a counter electromotive force. (See Counter Electromo- 
tive Force. Motors, Electric. Resistance, Spurious.) 

Ohmmeter. — A commercial galvanometer, devised by 
Ayrton, for directly measuring the resistance of any part of a 
circuit through which a strong current is flowing, by the de- 
flection of a magnetic needle. 

Ayrton's ohmmeter is represented diagrammatically in Fig. 
292. Two coils C C, and c c, of a short thick wire, and of a long 
thin wire, respectively, are placed at right angles to each other, 
and act on a soft iron needle situated as shown. The short 
thick wire coil C C, is connected in series with the resistance 
O, to be measured. The large fine wire coil, of known high 
resistance, is placed as a shunt to the unknown resistance. 



440 



A DICTIONARY OF ELECTRICAL 



Under these circumstances, it can be shown that the action 
on the needle is due to the ratio of the difference of potential 
at the terminals of the unknown resistance, and the current 

E 
strength in the thick wire coil, or, R — — , as may be deduced 

C 
from Ohm's law. 

The coils are so proportioned that the current when flowing 




TnssnsSOTwr^- 



Fig. 292. 
through the short thick wire moves the needle to the zero of 
the scale, while the long thin wire produces a deflection 
directly proportional to the resistance. 

Ohm's Law, — The strength of the current in any circuit, 

is directly proportional to 
the difference of potential, 
k or electromotive force in 
I that circuit, and inversely 
C proportional to the resis- 
tance of the circuit, i. e., is 
equal to the quotient aris- 
ing from dividing the elec- 



Hir* 



Fig. 



tromotive force by the resistance. 
Ohm's law is expressed algebraically, thus : 

E 
C = — . 
R 



WORDS, TERMS AND PHRASES. 441 

If the electro-motive force is given in volts, and the resis- 
tance in ohms, the formula will give the current strength 
directly in amperes. 

The resistance of any electric circuit, as for example that 
shown in Fig. 293, consists of three parts, viz.: 

(1) The resistance of the Source, r. 

(2) That of the Conducting Wires or Leads, r', and 

(3) That of the Electro-Receptive Device, r", energized by 
the current. Ohm's law applied to this case would be 

E 

C = . 

r -\- r' -f r" 
That is, the resistance of the entire series circuit is equal to 
the sum of the separate resistances. 

F" E 

Since C = — , (1) ; then E = C R, (2) ; and R = — , (3). 
R C 

But, since a current of one ampere is equal to one coulomb 
per second, then, in order to determine in coulombs the quan- 
tity of electricity passing in a given number of seconds, it is 
only necessary to multiply the current by the time in seconds, 
or Q = C T, (4). 

Hence, referring to the above equations (1), (2), (3) and (4), 
according to Ohm's law, 

(1) The current in amperes is equal to the electromotive 
force in volts divided by the resistance in ohms. 

(2) The electromotive force in volts is equal to the product 
of the current in amperes, and the resistance in ohms. 

(3) The resistance in ohms is equal to the electromotive 
force in volts divided by the current in amperes. 

(4) The quantity of electricity in coulombs, is equal to the 
current in amperes multiplied by the time in seconds. 

Open Circuit.— (See Circuit, Broken.) 

Optical Strain. — A deformation or alteration of volume 
produced in a plate of glass, or other transparent medium, by 
the action of any stress. 



442 A DICTIONARY OF ELECTRICAL 

The effect of this strain is shown by the action of the medium 
on a beam of plane polarized light. 

Optical Strain, Electro-Magnetic A strain 

produced in a plate of glass or other transparent medium by 
placing it in a magnetic field. (See Electro-Magnetic Stress. 
Magneto-Optic Rotation.) 

Optical strain, whether electrostatic or magnetic, or even me- 
chanical, often causes a medium to acquire the power of double 
refraction, or rotary polarization. (See Double Refraction, 
Electric. Magneto Optic Rotation.) 

Optical Strain, Electrostatic A strain pro- 
duced in a plate of glass, or other transparent solid, by subject- 
ing it to the stress of an electrostatic field. (See Electrostatic 
St?*ess.) 

To obtain the electrostatic stress, holes are drilled in the 
plate of glass, and wires from a Holtz machine or induction 
coil placed therein, the wires being separated by a thin layer of 
glass. The glass, on being traversed by a beam of plane po- 
larized light, rotates the plane of its polarization in the same 
direction as the glass would if subjected to a strain in the 
direction of the lines of electric force. (See Magneto- Optic 
Rotation.) 

Optics, Electro That branch of electricity which 

treats of the general relations that exist between light and 
electricity. 

The phenomena of electro-optics may be arranged under the 
following heads, viz.: 

(1) Electrostatic Stress, produced by an electrostatic field, 
causing an optical strain in a transparent medium, whereby 
such medium acquires either the property of rotating the 
plane of polarization of a beam of plane polarized light, or of 
doubly refracting light. 

(2) Electro-Magnetic Stress, produced by a magnetic field 
causing an optical strain in a transparent medium, whereby 
such medium acquires either the property of rotating the 



WORDS, TERMS AED PHRASES. 443 

plane of polarization, or of doubly refracting- light. (See Po- 
larization of Light. Double Refraction, Electric.) 

(3) Changes in the electric resistance of bodies caused by the 
action of light. (See Selenium Cell.) 

(4) The relation existing between the values of the index 
of refraction of a transparent medium and its specific induc- 
tive capacity. (See Refraction. Specific Inductive Capacity.) 

This relation has been shown to be as follows : 
The specific inductive capacity is approximately equal to the 
square of the index of refraction. 

(5) The relation existing between the velocity of light and 
the value of the ratio of the electrostatic and the electro-mag- 
netic units, thus giving a basis for an electro-magnetic theory 
of light. (See Light, Electro- Magnetic Theory of .) 

Ordinate*, Axis of (See Abscissas, Axis of.) 

Ores, Electric Treatment of (See Furnaces, 

Electric.) 

Organ, Electric A wind organ, in which the 

escape of air into the different pipes is electrically con- 
trolled. 

In an electric organ the keys, instead of operating levers 
as usual to admit the passage of air into the pipes, merely 
make the circuit of a battery through a series of controlling 
electro-magnets. With such an arrangement, the keyboard 
can be placed at any desired distance. 

Electric orgar>s have been constructed, in which a chemical 
or mechanical record is made of the notes struck by the per- 
former, as well as the musical value of these notes. By such 
a device the musical creations of a composer are permanently 
recorded in characters that are capable of interpretation by a 
compositor skilled in musical notation. 

Oscillating Discharge.— (See Discharge, Oscillating.) 
Oscillating Needle.— (See Needle of Oscillations.) 



444 A DICTIONARY OF ELECTRICAL 

Oscillation, Centre of The point, in a body- 
supported so as to swing like a pendulum, which is neither 
accelerated nor retarded during its oscillations. 

The centre of oscillation is always below the centre of grav- 
ity. The vertical distance between the centre of oscillation 
and the point of support of a pendulum, determines the virtual 
length of the pendulum and hence, its number of vibrations 
per second. (See Pendulum, Laws of.) 

Oscillations Electric The series of par- 
tial, intermittent discharges, of which the apparent instan- 
taneous discharge of a Leyden jar through a small resistance 
actually consists. 

These partial discharges produce a series of electric oscilla- 
tions of the current in the circuit of the discharge, which con- 
sist of a true to and fro, or backward and forward motion of 
the electricity. 

Osmose. — The unequal mixing of liquids of different dens- 
ities through the pores of a separating medium. 

If a solution of sugar and water be placed in a bladder, the 
neck of which is tied to a straight glass tube, and the bladder 
is then immersed in a vessel of pure water with the tube in a 
vertical position, the two liquids will begin to mix, the sugar 
and the water passing through the bladder into the pure water, 
and the pure water passing into the sugar and water in the 
bladder. This latter current is the stronger of the two, as will 
be shown by the water rising in the vertical glass tube. 

The stronger of the two currents is called the endosmotic 
current, and the weaker the exosmotic current. 

Osmose, Electric A difference of liquid level 

produced in two liquids placed on opposite sides of a diaph- 
ragm on the passage of a strong electric current through the 
liquids between two electrodes placed therein. 

The higher level is on the side towards which the current 
flows through the diaphragm, thus apparently indicating an 



WORDS, TERMS AND PHRASES. 445 

onward motion of the liquid with the current, cm* in other 
words, the liquid is higher about the kathode than the anode. 
The difference of level is the more marked when poorly con- 
ducting liquids are employed. 

As a converse of this, Quincke has shown that electric cur- 
rents arc set up when a liquid is forced by pressure through a 
porous diaphragm. The term diaphragm currents has been 
proposed for these currents. Their electro-motive force de- 
pends on the nature of the liquid, on the material of the dia- 
phragm, and on the pressure that forces the liquid through the 
diaphragm. (See Electro- Capillary Phenomena.) 

Output of Dynamo-Electric Machines. — The elec- 
tric power of the current generated by a dynamo-electric 
machine expressed in volt-amperes, or watts. 

S. P. Thompson suggests that dynamo-electric machines be 
rated as to their practical safe capacity in units of output of 
1,000 watts, or one kilo-watt. According to this, an 8-unit 
machine might give, say 100 amperes at a difference of poten- 
tial of 80 volts, or 2,000 amperes at a difference of potential of 
four volts. Such a unit would be far more expressive than 
the usual method of rating a machine as having a capacity of 
such and such a number of lights. 

Overtones. — Additional, faint tones, accompanying nearly 
every distinct musical tone, by the presence of which its pecu- 
liarity or quality is produced. (See Quality, or Timbre.) 

Ozone. — A peculiar modification of oxygen which pos- 
sesses more powerful oxydizing properties than ordinary 
oxygen. 

Ozone is now generally believed to be tri-atomic oxygen, or 
oxygen in which the bonds are closed, thus : 

O 

A 

o — o 

The peculiar smell observed when a torrent of sparks 



446 A DICTIONARY OF ELECTRICAL 

passes between the terminals of a Holtz machine, or a Ruhm- 
korff coil, is caused by the ozone thus formed. 

In a similar manner ozone is formed in the atmos- 
phere during the passage through the air of a flash of 
lightning. 

During the so-called electrolysis of water, some of the oxy- 
gen is given off in the form of ozone. The volume of the 
oxygen liberated is, therefore, somewhat less than half the 
volume of the hydrogen. 

Palladium. — A metal of the platinum group. 

Metallic palladium has a tin-white color, and, when polished, 
a high metallic lustre. It is tenacious and ductile, and, like 
iron, can be welded at a white heat. It is very refractory and 
possesses in a marked degree the power of absorbing or 
occluding hydrogen and other gases. It is not affected by 
oxygen at any temperature, nor readily affected by ordinary 
corrosive agents. 

Palladium Alloys.— Alloys of palladium with other 
metals. 

Palladium forms a number of useful alloys with various 
metals. Some of the alloys are as elastic as steel, are un- 
affected by moisture or ordinary corrosive agencies, and are 
entirely devoid of paramagnetic properties. 

These properties have been utilized by their discoverer, 
Paillard, in their employment for the hair-springs, escape- 
ments and balance wheels of watches, in order to permit the 
watches to be carried into strong magnetic fields without any 
appreciable effects on the rate of the watch. A number of 
careful tests made by the author, by long continued ex- 
posure of watches, thus protected by the Paillard alloys, 
in extraordinary fields, show that the protection thus 
given the watches enables them to be carried into the 
strongest possible magnetic fields without appreciably affect- 
ing- their rate, 



WORDS, TERMS AND PHRASES. 447 

The Paillarcl palladium alloys have the following- composi- 
tion, viz.: 

Alloy No. 1. 

Palladium _ 60 to 75 parts. 

Copper 15 to 25 " 

Iron.. 1 to 5 

Alloy No. 2. 

Palladium.. .50 to 75 " 

Copper 20 to 30 

Iron 5 to 20 

Alloy No. 3. 

Palladium. ..65 to 75 

Copper.. 15 to 25 " 

Nickel lto 5 " 

Gold.. lto 2% " 

Platinum % to 2 

Silver 3 to 10 " 

Steel.... lto 5 " 

Alloy No. 4. 

Palladium 45 to 50 " 

Silver.. 20 to 25 •« 

Copper _ 15 to 25 

Gold... 2to 5 " 

Platinum 2 to 5 " 

Nickel. 2to 5 " 

Steel 2to 5 " 

The great value of these alloys, when employed for the hair- 
springs of watches, arises not only from their non-magnetiz- 
able properties, and, their inoxidizability, but particularly 
from the fact that their elasticity is approximately the same 
for comparatively wide ranges of temperature. 

Pane, Magic A sheet of glass covered with pieces 

of tin foil with small spaces between them pasted in some de- 
sign on the glass. 

On the discharge of a Leyden jar through these metallic 



448 A DICTIONARY OF ELECTRICAL 

pieces, the design is seen as a series of minute sparks that 
bridge the spaces between the adjacent pieces of foil. 

Pantelegraphy, or Facsimile Telegraphy.— A 

system for the telegraphic transmission of charts, diagrams, 
sketches or written characters. (See Telegraphy, Facsi- 
mile.) 

Paper Carbons. — Carbon, of textile or fibrous origin, 
obtained from the carbonization of paper. 

The carbonization of paper is readily effected by submitting 
it to the prolonged action of a high temperature while out of 
contact with air. 

For this purpose the paper is packed in retorts or crucibles, 
and covered with lamp-black, or powdered plumbago, in 
order to exclude the air. 

Since paper consists of a plane of material uniformly thin 
in one direction, formed almost entirely of fibres of pure cel- 
lulose, the greatest length of which extend in a direction 
nearly parallel to that in which the paper is uniformly thin, 
it is clear that sheets of this substance, when carbonized, 
should yield flexible carbons of unusual purity and electrical 
homogeneity, since such carbons are structural in character, 
and are uniformly affected by the heat of carbonization, to an 
extent that would be impossible by the carbonization of any 
material in a mass. 

Paper Perforator. — An apparatus employed in systems 
of automatic telegraphy for punching in a fillet of paper, 
circular or elongated spaces that produce the dots and dashes 
of the Morse alphabet, when the fillet is drawn between metal 
terminals that form the electrodes of a battery. (See Teleg- 
raphy, Automatic.) 

Parabolic Reflector. — A reflector, or mirror, the reflect- 
ing surface of which is a paraboloid, or such a surface as 
would be obtained by the revolution of a parabola about its 
axis. 



WORDS, TERMS AND PHRASES. 449 

A parabolic curve, which may be regarded as a section of a 
parabola, is shown in Fig. 294. A parabola has the following- 
properties : If lines F P, F P, etc., be drawn from the point 
F, called the focus, to any point, P, P, etc., in the curve, and 
the lines Pp, Pp, Pp, etc., be then drawn severally parallel to 
the axis, V M, then all such angles, F Pp, F Pp, will be 
bisected by verticals to tangents at the point P, P, and P. 

Therefore, if a light be placed at the focus of a parabolic 
reflector, all the light reflected will pass off sensibly parallel 
to the axis V M. 

In locomotive head lights, a lamp is placed at the focus of a 
parabolic reflector, and the parallel beam so obtained utilized 
for the illumination of the track. In a search 
light, an electric arc lamp is placed in a para- 
bolic reflector, or at the focus of a lens. 

A parabolic reflector, such as is used for 
search lights, is shown in Fig. 295. A fo- 
cussing arc lamp must be used for this pur- v ' 
pose, so as to maintain the voltaic arc at ' 
the focus of the parabolic reflector, notwith- 
standing the consumption of the carbons. 

Parafflnc. — The name given to various 
solid hydrocarbons, of the marsh-gas series, Fig. 2%. 

that are derived from coal oil or petroleum by the action of 
nitric acid. 

Parafine possesses excellent powers of insulation, and forms 
a good dielectric medium. Dried wood, boiled in melted par- 
afhne, forms a fair insulating material. 

Paragreles. — Lightning rods, intended to protect fields 
against the destructive action of hail. (See Hail, Assumed 
Electrical Origin of.) 

It was formerly believed that hail is caused by electricity. 
It is now generally believed that the electricity in hail storms 
is caused by the hail. It will therefore readily be understood 
that paragreles can afford no real protection. 



pz 


w 


P 


w 


^7 P 


p 




p'AI p 


P 




\i v 


V 


M 




f 
\ p 


p 




r 


\ P 


p 




)A p 


p 






w 





450 



A DICTIONARY OF ELECTRICAL 



Parallax. — The apparent angular displacement of an ob- 
ject when seen from two different points of view. 

In reading the exact division on a scale to which a needle 
points, care must be taken to look directly down on the needle, 

and not sideways, so as to 
avoid the error of displace- 
ment due to parallax. 

Parallel Circuit. — A 

name sometimes applied to 
circuits connected in multiple- 
arc. (See Circuits, Varieties 
of.) 

Parallelogram of 
Forces. — (See Forces, Par- 
allelogram of.) 

Paramagnetic. -Sub- 
stances possessing the proper- 
ties ordinarily recognized as 
magnetic. 

Substances possessing the 
power of concentrating the 
lines of magnetic force on 
them. 

Paramagnetic is a term em- 
ployed in contra-distinction 
to diamagnetic. (See Dia- 
magnetic.) A paramagnetic 
substance, cut in the form 
of a bar whose length is much greater than its breadth and 
thickness, when suspended in a magnetic field in the manner 
shown in Fig. 296, will take up a position of rest with its 
greatest length in the direction of the lines of force, i. e., 
will point axially. In other words the lines of force will so 
pass through the paramagnetic substance as to reduce the 
magnetic resistance of the circuit as much as possible, 




Fig. 295. 



WORDS, TERMS AND PHRASES. 



451 



Paramagnetic substances, therefore, concentrate the lines of 
force on them. (See Resistance, Magnetic.) 

Diamagnetic substances, on the contrary, placed as shown 
in Fig. 296, assume a position of rest with their least dimen- 
sions in the direction of the lines of force, i. e., the}' point 
equatorially. This is the position in which they are placed by 
the lines of force, in order to ensure the least magnetic resist- 
ance in the circuit of these lines. The magnetic resistance of 
diamagnetic substances is great as compared with that of 
paramagnetic substances. - 

The term ferro-magnetic has been proposed for paramag- 
netic. If another term be required, which 
is doubtful, sidero-magnetic proposed by f^\ 

S. P. Thompson, would be far prefer- 
able. (See Ferro-Magnetic. Sidero-Mag- 
netic.) 

Tyndall believes that the magnetic po- 
larity possessed by diamagnetic substances 
is a distinct polar force, different in its 
nature from ordinary magnetiism. (See 
Polarity, Diamagnetic.) 

Paramagnetism. — The magnetism 
of a paramagnetic substance. 

Parasitical Currents.— (See Cur- 
rents, Eddy, Foucault, or Local.) 

Paratoniieres.— A French term for 
lightning rods, sometimes employed in English technical 
works. 

Lightning rod would appear to be the preferable term. 

Partial Earth. (See Earths.) 

Passive State. — The condition of a metallic substance 
in which it may be placed in liquids that would ordinarily 




Fig. 296. 



452 A DICTIONARY OF ELECTRICAL 

chemically combine with it, without being attacked or cor- 
roded. 

It is very doubtful whether metallic bodies can be properly 
regarded as possessing an actual passive state. Iron, for 
example, which is one of the metals that is said to be capa- 
ble of assuming this so called passive state, can be placed 
in this condition by immersing it for a few moments in concen- 
trated nitric acid, and subsequently washing it. It will then, 
unlike ordinary iron, neither be attacked by concentrated 
nitric acid, nor will it precipitate copper from its solutions. 
This condition is now generally believed to be due to the for- 
mation of a thin coating of magnetic oxide on its surface. 

Many of the instances of the so-called passive state are 
simply cases of the well known electrical preservation of 
metals that form the negative element of a voltaic combina- 
tion, under which circumstances the positive element only of 
the voltaic couple is chemically attacked by the electrolyte. 
(See Cell, Voltaic. Metals, Electrical Preservation of.) 

P. D. or p. d. — A contraction frequently employed for 
difference of potential. (See Difference of Potential.) 

Peltier E fleet. —(See Effect, Peltier.) 

Pendulum, Electric A pendulum so arranged 

that, in its to-and-fro motions, it sends electric impulses over 
a line, either by making and breaking contacts, or such in 
which the to and fro movements are maintained by electric 
impulses. 

Such pendulums are employed in systems for the electrical 
distribution of time. 

Sometimes, instead of using true pendulums for such pur- 
poses, coils, or contact points, mounted on the ends of flexible 
bars of steel called reeds, or on tuning forks, are often used 
for the purpose of establishing currents, or modifying the cur- 
rents that are already passing in a circuit. The movement 
of a magnetic diaphragm, as in the case of a telephone 



WORDS. TERMS AND PHRASES. 453 

diaphragm, towards and from a coil of wire is another illustra- 
tion of an electric pendulum. 

Pendulum, Laws of The laws which ex- 
press the peculiarities of the motion of a simple pendulum. 

A simple pendulum is one in which the entire weight is con- 
sidered as concentrated at a single point, suspended at the 
end of a weightless, inflexible, and inextensible line. 

The following are the laws of the simple pendulum : 

(1) Oscillations of small amplitude are approximately 
isochronous: that is, are made in times that are sensibly 
equal. (See Amplitude of Vibration. Isochronism.) 

(2) In pendulums of different lengths, the 
duration of the oscillations is proportional to 
the square root of the length of the pendulum. 

(3) In the same pendulum, the length being 
preserved invariable, the duration of the 
oscillation is inversely proportional to the 
square root of the intensity of gravity. 

The intensity of gravity at any latitude, may 
be determined by the number of oscillations of Fig . 297. 
a pendulum of a given length. In the same manner the inten- 
sity of a magnetic field, or the intensity of magnetization of 
a magnet, may be determined by the needle of oscillation. 
by observing the number of oscillations a needle makes in 
a given time when disturbed from its position of rest. (See 
Needle of Oscillation.) 

Since a simple physical pendulum is a physical impossibility, 
the virtual length of a pendulum, that is, the vertical distance 
between its point of support to the centre of oscillation is 
taken as the true length of the pendulum. 

If the irregularly shaped body, shown in Fig. 297, whose cen- 
tre of gravity is at G, is made to swing like a pendulum, either 
on S, or O, its oscillations will be performed in equal times, and 




454 A DICTIONARY OF ELECTRICAL 

the body will act as a simple pendulum, whose virtual length 
is S O. 

If, while suspended at S, it be struck at O, it will oscillate 
around S, witbout producing- any pressure on the supporting- 
axis at S, on which it turns. If floating entirely submerged 
in a liquid, a blow at O would cause it to move in a straight 
line, in t lie direction of tbe blow, without rotation. 

The point O, is called the centre of percussion, or the centre 
of oscillation. The centre of oscillation is always below the 
centre of gravity. 

Pen, Electric A device for manifold copying, in 

which a sheet of paper is made into a stencil by minute per- 
forations obtained by a needle driven by a small electric motor. 
The stencil is afterwards employed in connection with an inked 
roller for the production of any required number of copies. 

Mechanical pens are constructed on the same principle, the 
perforations being obtained by mechanical instead of by 
electric power. 

Percussion, Centre of That point in a body, 

suspended so as to move as a pendulum at which a blow 
would produce rotation, but no forward motion, or motion 
of translation. 

Periodicity ol Auroras and Magnetic Storms. — 

Observed coincidences between the occurrence of auroras and 
magnetic storms, and sun spots. 

The periodical occurrence of auroras, or magnetic storms, 
both as to frequency and intensity, which, occuring at periods 
of about eleven years apart, corresponds to the well-know 
eleven-year sun-sjjot period. 

It also agrees with a variation in the magnetic declination of 
a place which, according to Sabine, occurs once in every 
eleven years. 

Permanent Magnet. — (See Magnet, Permanent.) 



WORDS, TERMS AND PHRASES. 



455 



Permanent State of Charge of Telegraph Line. 

—(See State, Permanent.) 

Permeability, Magnetic The ease afforded 

by any substance to the passage through it of lines of mag- 
netic force. 

The magnetic permeability of paramagnetic substances is 
much less than that of diamagnetic substances. A substance 
of great magnetic permeability has small magnetic resistance, 
or possesses small magnetic reluctance to magnetization. (Sec 
Paramagnetic. Diamagnetic. Magnetic Reluctance.) 




HIIIIIIIIHIIIIIIIIIIIIIIIIIHIIIIIIIIIIIIIIII Ullllllllll Illllllll lllllllllllllllllllllllMllllllllllDIIIIIIIIIIIIIIHim 



-(See Elec- 



Fig. 298. 

Phenomena, Electro Capillary 

tro-Capillary Phenomena.) 
Pherope or Telephote.— (See Telephote.) 

Phial, Ley den (See Jar, Ley den.) 

Philosopher's Egg.— (See Discharge, Convective.) 
Phonantograph.— An apparatus for the automatic pro- 
duction of a visible tracing of the vibrations produced by any 
sound. 



456 



A DICTIONARY OF ELECTRICAL 



PhonautogTaphic apparatus consists essentially of devices 
by which the sound waves are caused to impart their to-and- 
fro movements to a diaphragm at the centre of which a pencil 
or tracing' point is attached. The record is received on a sheet 
of paper, or wax, or on a smoked glass or other suitable sur- 
face. 

Leon Scott's Phonautograph, which is among* the forms 
best known, consists of a hollow conical vessel A, Fig. 298, with 
a diaphragm of parchment stretched tightly like a drum-head 
over its smaller aperture B. A tracing point, attached to the 




Fig. 299. 

centre of the diaphragm, traces a sinuous line on the surface 
of a soot-covered cylinder 0, that is uniformly rotated under 
the tracing point. As the cylinder is advanced a short dis- 
tance with every rotation, a sinuous spiral line is traced on the 
surface. 

Phonic Wheel. — A wheel to which is attached a circular 
table of contact points, that is maintained in synchronous 
rotation by means of a timed series of electric impulses sent 
over a line. 



WORDS, TERMS AND PHRASES. 45? 

The phonic wheel was invented by La Cour, but was first 
put into successful operation in multiplex telegraphy by 
Delany in his system of Synchronous Multiplex Telegraphy. 
(See Telegraphy, Synchronous, Multiplex.) Delany obtains 
the exact synchronism of the phonic wheel by a series of cor- 
recting electric impulses, automatically sent over the line on 
the failure of the phonic wheel at either end of the line to 
exactly synchronise with that at the other. 

Phonograph. — An apparatus for the reproduction of 
articulate speech, or of sounds of any character, at any in- 
definite time after their occurrence and for any number of 
times. 

In Edison's phonograph the voice of the speaker, received 
by an elastic diaphragm of thin sheet iron, or other similar 
material, is caused to indent a sheet of tin-foil placed on the 
surface of a cylinder C, Fig. 299, that is maintained at a uni- 
form rate of rotation by the crank at W. In the form shown, 
the motion is by hand, In a later improved form the cylinder 
is driven by means of an electric motor, or b} T clockwork. 

In order to reproduce the speech or other sounds the phono- 
gram record is placed on the surface of a cylinder similar to 
that on which it was received, (or is kept on the same surface), 
and the tracing point, placed ai the beginning of the record 
and being maintained against it by gentle pressure, is caused, by 
the rotation of cylinder, to follow the indentations of the pho- 
nogram record. As the point is thus moved up and down the 
hills and hollows of the record surface, the diaphragm to which 
it is attached is given a to-and-fro motion that exactly corres- 
ponds to the to-and-fro motion it had when impressed 
originally by the sounds it has recorded on the phonogram 
record. A person listening at this diaphragm will therefore 
hear an exact reproduction of the sounds originally uttered. 

In this manner, the voices of relatives, distinguished sing- 
ers, or statesmen can be preserved for future generations. 



458 



A DICTIONARY OF ELECTRICAL 



In Edison's improved phonograph, the record suuface con- 
sists of a cylinder of hardened wax. The motion of the cylin- 
der is obtained by means of an electric motor. Two diaphragms 
are used, one for recording, and one for reproducing. As 
shown in Fig. 300, the recording diaphragm is in position 
against the cylinder. The recording diaphragm is made of 
malleable glass. The reproducing diaphragm is formed of 
bolting silk covered with a thin layer of shellac. 




Fig. 300. 

In the Graphophone of Bell and Tainter, the point at- 
tached to the diaphragm is caused to cut or engrave a cylinder 
of hardened wax. Two separate diaphragms are employed, 
one for speaking, and the other for hearing. 

The surface is made of a mixture of beeswax and paraffine. 
A uniformity of rotation of the cylinder is obtained by means 



WORDS, TERMS AND PHRASES. 



459 




Fig. 301. 



460 



A DICTIONARY OF ELECTRICAL 



of a motor provided with a suitable governor. An ordinary 
conversation of some five minutes, it is claimed, can be 
recorded on the surface of a cylinder 6 inches long and l 1 ^ 
inch in diameter. 

In the Gramophone of Berliner, a circular plate of metal, 
covered with a film of finely divided oil or grease, receives the 




Fig. 303. 

record in a sinuous, spiral line. This record is subsequently 
etched into the metal by any suitable means, or is photog- 
raphically reproduced on another sheet of metal. 

Glass covered with a deposit of soot is sometimes employed 
for the latter process. The apparatus is shown in Fig. 302, as 
arranged for the reproduction of speech. 

In Mr. Berliner's apparatus, the record surface is impressed 
by a point attached to the transmitting* diaphragm, in a direc- 
tion parallel to the record surface, and not, as in the instrument 



WORDS, TERMS AND PHRASES. 461 

of Mr. Edison, in a direction at right angles to the same. This 
method, would appear to be the best calculated for the 
more exact reproduction of articulate speech, since it permits 
comparatively loud speaking or singing, without interfer- 
ing with the quality of the reproduced sounds. Since the re- 
sistance to indentation, or vertical catting, increases more 
rapidly than the increase in the amplitude of vibration (See 
Amplitude of Vibration) of the cutting point, it follows that 
the louder the sounds recorded by the phonograph or grapho- 
phone, the less complete would be the quality of the repro- 
duced sounds, or the less the probability of the peculiarities 
of the speaker's voice being recognized. In order to avoid 
this, the speaker in the phonograph and the graphophone 
speaks in an ordinary conversational tone only. 

For purposes of dictation, and most commercial purposes, 
this is rather an advantage than otherwise. 

Phonograph, Graphophone, or Gramophone 
Rceords. — Records produced in a phonograph, grapho- 
phone, or gramophone, for the subsequent reproduction of 
audible, articulate speech. 

Phonozenograph. — An instrument devised by De Feltre 
to indicate the direction of a distant sound. 

A Deprez-D' Arson val galvanometer, a Wheatstone's bridge, 
and a microphone of peculiar construction, are placed in the 
circuit of a voltaic battery, and a receiving telephone. The 
observer determines the direction of the distant sound by 
means of the sounds heard under different conditions in the 
telephone. 

PhoiUograph. — A name proposed for an electro-thermal 
recording telephone devised by Irish. 

Phosphore§cenee. — The power of emitting light, or be- 
coming luminous by simple exposure to light. 

Bodies that possess the property of phosphorescence, when 
exposed to a bright light acquire the power of continuing 



462 A DICTIONARY OF ELECTRICAL 

to emit light, when carried into the dark, for periods varying 
from a few seconds to several hours. The diamond, barium and 
calcium sulphides, dry paper, silk, sugar, and compounds of 
uranium, are examples of phosphorescent substances. 

A phosphorescent body generally emits light of the same 
character as that it absorbed when exposed to the exciting 
light, That there is an actual absorption, is seen from the 
fact that the light which has passed through a fluorescent 
solution, fails to produce fluorescent effects in a similar solu- 
tion. A selective absorption has, therefore, been effected. 

The effects of phosphorescence appear to be due to sympa- 
thctic vibrations set up in the molecules of the phosphores- 
cent body by the exciting light. (See Sympathetic Vibrations.) 

In some cases, however, that are not exactly understood, 
the wave length of the emitted light is more rapid than that 
of the exciting light. 

The phenomena of fluorescence are now generally believed 
to be due to the phosphorescence of the body during its ex- 
posure to the light, The portions traversed by the light are 
thus temporarily rendered luminous. (See Fluorescence.) 

The fire-fty, the glow-worm, and decaying animal or vege- 
table matter, exhibit a species of phosphorescence, that ap- 
pears to be due to the actual oxidation, or gradual burning 
of a peculiar, specific, chemical substance. 

Phosphorescence may therefore be divided into two classes, 
viz. : 

(1) Physical Phosphorescence, or that produced, by the 
actual impact of the light, and, 

(2) Chemical Phosphorescence, or that caused by an actual 
chemical combination, or the combustion of a specific sub- 
stance. 

Phosphorescent paints for rendering the position of a push 
button, electric call, match safe, or other similar object visible 
at night, consist essentially of sulphides of calcium or 
barium, or of mixtures of the same. 



WORDS, TERMS AND PHRASES. 



463 



Phosphorescence, Electric 



-Phospho- 



rescence caused in a substance by the passage of an electric 
discharge. 

The phosphorescent material is placed in an exhausted glass 
tube, as shown in Fig. 303, and submitted to the action of a 
series of discharges, as from a Ruhmkorff coil, or Holtz 
machine. The violet blue light of such discharge is very 
efficient in producing phosphorescence. Phosphorescence is 
thus effected by subjecting the phosphorescent material to 
the molecular bombardment which thus occurs in a high 
vacuum. (See Bombardment, Molecular.) 

Photometer. — An apparatus for measuring the intensity 
of the light emitted by any luminous source. 

There are vari- 
ous methods for 
measuring the in- 
tensity of a beam 
of light passing 
through any giv- 
en space, or emitt- 
ed from any lum- 
inous source; 
these methods 
are embraced in Fig. SOS. 

the use of the following apparatus : 

(1) Calorimetric Photometer, in which the light to be meas- 
ured is absorbed by the face of a thermo-electric pile and the 
electric current thereby produced is carefully measured. 
Since obscure radiation, or heat will also thus produce an 
electric current, it is necessary to first absorb all the heat by 
passing the beam of light through an alum cell. 

(2) Actinic, or Chemical Photometers, in which the intensity 
of the light is estimated by a comparison of the depth of 

oloration produced on a fillet of photographic paper under 




464 



A DICTIONARY OF ELECTRICAL 



similar conditions of exposure to a standard light, and the 
light to be measured. 

The combination of pure hydrogen and chlorine, or the de- 
composition of pure mercurous chloride, have been employed 
for the purpose of determining the intensities of two lights by 
measuring th« amount of chemical decomposition effected. 

(3) Shadoiv Photometers, in which a shadow produced by 
the light to be measured is compared with a shadow produced 
by a standard candle. (See Candle, Standard.) 




Fig. SOU. 

Rumford's photometer, shown in Fig. 304, is an example 
of this form of instrument. The standard candle, shown at L, 
casts a shadow C", of an opaque rod C, on the screen at B. 

The light to be measured L', is moved away from the screen 
until its shadow C, on the screen at A, is judged by the eye to 
be of the same depth. The distance between the screen and 
the lights is then measured in straight lines. The relative in- 
tensities of the two lights are then proportional to the squares 
of their distances. If, for example, the candle be at 10 inches 



WORDS, TERMS AND PHRASES. 465 

from the screen, and the lamp at 40 inches, then the intensities 
are as 10 3 : 40 2 or as 100 : 1600, or the lamp is a 16 candle-power 
lamp. 

This photometer is based on the fact that the shadow of each 
source is illumined by the light of the other source. 

(4) Translucent Disc Photometers. — The light to be meas- 
ured and a standard candle are placed on opposite sides of a 
sheet of paper the centre of which contains a grease spot. 
The standard candle is kept at a fixed distance from the paper 
and the other light is moved towards or from the paper 
until both sides of the paper are judged to be equally illu- 
mined. 

In Bunsen's photometer a vertical sheet of paper with a 
grease spot at its centre, is exposed to the illumination of a 
standard candle on one side, and the light to be measured on 
the other. 

The sheet of paper is placed inside a dark box provided 
with two plane mirrors placed at such an angle to the paper 
that an observer can readily see both sides of the paper at the 
same time. 

This box can be slid along a graduated, horizontal scale, 
towards, or from, the light to be measured, and carries with it 
the standard candle mounted on it at a constant distance of 10 
inches. If the box is too near the light to be measured, the 
grease spot appears brighter on the side of the sheet of paper 
nearest the candle. If too near the candle, it appears brighter 
on the side of the sheet of paper nearest the light to be 
measured. The position in which the spot appears equally 
bright on both sides, is the position in which it is equally 
illumined, and the relative intensities of the two lights are then 
directly as the squares of their distances from the sheet of 
paper. 

Shadow, and translucent disc, photometers being dependent 
on equal illumination, are reliable only when the color of the 
lights compared is the same. For the determination of the 



466 A DICTIONARY OF ELECTRICAL 

photometric intensity of very bright lights, the standard 
candle is replaced by a carcel lamp, a standard gas jet, or by 
the light emitted by a given mass of platinum, heated by a 
given current of electricity. (See Carcel Lamp. Carcel 
Standard Gas Jet. Platinum Standard Light.) 

Preece's photometer belongs to the class of translucent 
disc photometers. A tiny incandescent lamp is placed in a 
box, the top of which has a white paper screen on which is 
a grease spot. The box is placed in the street where the in- 
tensity of illumination is to be measured, and the intensity of 
the light of the incandescent lamp is varied until the grease 
spot disappears. The current of electricity then passing 
through the incandescent lamp acts as the measure of the 
illumination. 

In the case of the shadow photometer, or of Bunsen's photo- 
meter, if the intensity of illumination is the same, the relative 
intensities of the two lights may be determined as follows : 

Calling I, and i, respectively the relative intensities of the 

standard light, and the light to be measured, and D, and d, 

their respective distances from the screen, then 

I : % : : D 2 : d 2 , or I x d* = i x D 2 ; 

/ d 2 \ 
that is, i = I ( — ) • 
VD 2 / 

/d 2 \ 
Or, the intensity of the light to be measured is (— J times 

the intensity of the standard light. 

If for example D, and d, represent 10 and 100 inches, respec- 
tively, the intensity of i is 100 times the intensity I, the 
standard light. 

(5) Dispersion Photometers. — A class of photometers in 
which, in order to more readily compare or measure a very 
bright or intense light, like that of an arc lamp, the intensity 
of the light is decreased by dispersion by a readily measurable 
amount. 

Ayrton & Perry's Dispersion Photometer. — A photometer 
in which, in order to bring an intensely bright light, like 



WORDS, TERMS AND PHRASES. 



467 



an electric arc light, to such an intensity as will permit it to 
be readily compared with a standard candle, its intensity 
is weakened by its passage through a diverging (concave) 
lens. 

Ayrton & Perry's dispersion photometer is shown in two 
different positions, Figs. 305 and 306. The apparatus is 
supported on a tripod stand E, arranged so as to obtain 
exact levelling. A plane mirror H, movable around a pin 
placed directly under its centre, can be rotated and thus reflect 
the light after its passage through the diverging lens, while 
still maintaining its distance from the electric light. 




Fig. 305. 

The horizontal axis of this mirror is inclined 45° to its 
reflecting surface in order to avoid errors arising from varying 
absorption at different angles of reflection. 

The inclination of the beam to the horizontal is indicated by 
means of an index attached to the' mirror and moving over 
the graduated circle G. 

A black rod A, casts its shadow on a screen of white blot- 
ting paper B, A standard candle, placed in the holder D, 



468 



A DICTIONARY OF ELECTRICAL 



casts its shadow alongside the shadow cast by the electric 
light. The lens is now displaced until the shadow of the 
electric light is of the same intensity as that of the candle, 
when viewed successively through sheets of red and green 
glass. 

A graduated scale serves to mark the distance of the candle 
and of the lens from the screen, from which data the intensity 
of the electric light may be calculated. 




Fig. 306. 

(6) Selenium Photometers. — Instruments in which the rela- 
tive intensities of two lights are determined by the effects pro- 
duced on a selenium resistance. 

In Siemens' selenium photometer a selenium cell is em- 
ployed in connection with an electric circuit for determining 
the intensity of light. 

The tube A B, Fig. 307, is furnished at A with a dia- 
phragm, and at B with a selenium plate, connected by wires, 
G G, with the circuit of a battery and a galvanometer. 

A graduated scale L M, bears the standard candle N. 



WORDS, TERMS AND PHRASES. 



469 



The tube A B is capable of rotation on the vertical axis F. 
A reflecting- mirror-galvanometer is used in connection with 
the selenium photometer. The light to be measured is 
placed at right angles to the scale L M, and the tube A B 
directed towards it, and the galvanometer deflection com- 
pared with the deflection obtained when turned towards the 
standard candle. 

(7) Gas-Jet Photometers.— Instruments in which the candle 
power of a gas jet is determined by measuring the height at 

which the jet burns when under unit conditions of volume 

and pressure. 




Fig. 807. 

In determining the candle power of an intense light like 
the electric arc light, a large gas light is used intsead of a 
standard candle, and the photometric power of this gas light 
is carefully determined by comparison with a gas-jet pho- 
tometer. (See Car eel, Standard, Gas Jet.) 

Photoplione.— An instrument invented by Bell for the 
telephonic transmission of articulate speech along a ray of 
light instead of along a conducting wire. 

A beam of light, reflected from a diaphragm against which 



470 A DICTIONARY OF ELECTRICAL 

the speaker's voice is directed, is caused to fall on a Selenium 
resistance inserted in the circuit of a voltaic battery, and a 
telephone. The changes thus effected in the resistance of 
the circuit by the varying amounts of light reflected on 
the selenium from the moving diaphragm, produce in the 
receiving telephone, a series of to-and-fro movements, similar 
to those impressed on the transmitting diaphragm. One 
listening at the telephone can hear whatever has been spoken 
at the transmitting diaphragm. Telephonic communication 
can therefore by such means be carried on along a ray or 
beam of light, theoretically through any distance. (See Selen- 
ium, Resistance.) 

A block of vulcanite and many other substances may be 
used as the receiver, since it has been discovered that a rapid 
succession of flashes of light produces an audible sound in 
small masses of these substances. The term Sonorescence has 
been proposed for such a property. (See Sonorescence.) 

Photophore, Trouve's An apparatus in 

which the light of a small incandescent electric lamp is em- 
ployed for purposes of medical exploration. 

A small incandescent lamp is placed in a tube containing a 
concave mirror and a converging lens. 

Phototelegraphy, or Telephotography.— The elec- 
tric production of pictures, writing, charts, or diagrams at a 
distance. (See Telejrfwtograjihy.) 

Photo- Voltaic Effect. — The change in the resistance of 
selenium or other substances effected by their exposure to 
light. (See Selenium Cell.) 

Physiology, Electro (Sec Electro-Physi- 
ology.) 

Piano, Electric A piano in which the strings 

are struck by hammers actuated by means of electro-mag- 
nets, instead of by the usual mechanical action of levers. 



WORDS, TERMS AND PHRASES. 471 

Electric piano-action is mainly useful in permitting* the in- 
strument to be played at any distance from the performer. 
It is also of value from the ease it affords in recording the 
piece played. 

It fails, however, to properly preserve the various modula- 
tions of force so requisite for brilliant instrumentation. 

Pickle. — An acid solution in which metallic objects are 
dipped before being galvanized, or electroplated, in order to 
thoroughly cleanse their surfaces. 

The pickle used for the preparation of iron for galvaniza- 
tion is a weak solution of sulphuric acid in water. Vari- 
ous acids, or acid liquids, are employed for that thorough 
cleansing of metallic surfaces so necessary in order to ensure 
an even, uniform, adherent coating of metal by the process 
of electro-plating. (See Electro-Plating.) 

Pile, Dry ■ — A voltaic battery, consisting of 

numerous voltaic couples formed of discs of paper co veved on 
one side with zinc-foil, and on the other with black oxide of 
manganese. (See Dry Pile.) 

Pile, Matteucci's Muscular (See Muscular 

Pile, Matteucci's.) 

Pile, Thermo-Electric A battery consisting 

"of a number of thermo-electric couples connected so as to 
form a single electric source. (See Thermo-Electric Battery.) 

Pile, Voltaic A battery consisting of a 

number of voltaic couples connected so as to form a single 
electric source. 

A form similar to Volta's original pile, consisting of alternate 
discs of copper and zinc, separated from each other by discs of 
wet cloth, and piled on one another, so as to form a number of 
separate voltaic couples connected in series, is showfi in 
Fig. 308. The thick plates marked Zn, are of zinc ; the 
copper plates, marked Cu are much thinner. The discs 
of moistened cloth are shown at d d. One end of such a 



472 



A DICTIONARY OF ELECTRICAL 



pile, would then be terminated by a plate of copper, and the 
other by a plate of zinc. The copper end forms the positive 
electrode, and the zinc end the negative electrode. (See Cell, 
Voltatic, Polarity of Electrodes.) 

Pith.— A light, cellular ma- 
terial forming- the central por- 
tions of most exogenous plants. 
An excellent pith, suitable for 
electrical purposes, is furnished 
by the dried wood of the elder- 
berry. 

Pith-Ball Electroscope. 

— An electroscope which shows 
the presence of a charge by 
the repulsion of two similarly 
charged pith balls. (See Elec- 
troscope.) 

Any two pith balls, suspended 
by conducting threads, but in- 
sulated from the earth, will 
serve as an electroscope. 

Pith Balls.— Two balls of 

pith, suspended by conducting 

threads of cotton to insulated 

conductors, and employed to 

show the electrification of the 

same,by their mutual repulsion. 

The pith balls connected with 

Fig. 308. the insulated cylinder A B, 

Fig. 309, not only show the electrification of the cylinder, but 

serve also to roughly indicate the peculiarities of distribution 

of the charge thereon. 

Pivot Suspension. — The suspension of a needle or mag- 
net, by a pivot, as distinguished from suspension by a thread. 
(See Suspension, Methods of.) 




WORDS, TERMS AND PHRASES. 



473 



Plant ». Electricity of —Electricity produced 

naturally by plants during- their vigorous growth. 

DuBois-Reymond and others, have shown that plants while 
in a vigorous vital state, are active sources of electricity. If 
one of the terminals of a galvanometer be inserted into a fruit 
near its stem, and the other terminal into the opposite part of 
the fruit, the galvanometer at once shows the presence of an 
electric current. 

Buff has shown that the roots and interior portions of plants 
are always negatively charged, while the flowers, fruits and 
green twigs are positively charged. 

Plant tissue or fibre, like the muscular fibre of animals, 
exhibits in many cases a true contraction on the passage 
through it of an electric current. This is seen in the mimosa 
sensitiva, or sensitive fern ; in the Venus' fly trap ; and in 
several other species of plants. 





Fig. 309. 

Plate Condenser. — (See Condenser or Accumulator.) 

Plating Bath, Electro (See Bath, Electro- 
Plating.) 

Plating, Electro The depositing of a plating 

or coating of one metal on the surface of another metal, or on 
any conducting surface, by the action of electricity. — (See 
Electro-Plating. ) 

Platinoid. — An alloy consisting of German silver with 
one or two per cent, of metallic tungsten. 



474 A DICTIONARY OF ELECTRICAL 

This alloy is suitable for use in resistance coils on account 
of the comparatively small influence produced on its electric 
resistance by changes of temperature. (See Coils, Resistance), 

Its resistance is 60 per cent, higher than that of German 
silver. 

Platinum. — A refractory and not readily oxidizable metal, 
of a tin white color. 

The coefficient of expansion of platinum by heat is nearly 
that of ordinary glass. Platinum is, therefore, much employed 
for the leading-in conductors of an incandescent lamp. 

Platinum Black.— Finely divided platinum that pos- 
sesses, in a marked degree, the power of absorbing or occlud- 
ing gases. 

Platinum black is obtained by the action of potassium hy- 
drate on platinum chloride. Unlike metallic platinum it is of 
a black color. 

Platinum-Silver Alloy.— An alloy used for resistance 
coils, consisting of one part of platinum and two parts of silver. 

Platinum Standard Light.— The light emitted by a 
surface of platinum, one square centimetre in area, at its tem- 
perature of fusion. 

Plow. — The sliding contacts connected to the motor of an 
electric streetcar, and placed within the slotted underground 
conduit, and provided for the purpose of taking off the 
current from the electric mains placed therein, as the 
contacts are pushed forwards over them by the motion of 
the car. 

Similar contacts, placed in the rear of the motor car and 
drawn after the train, form what is technically known as the 
sled, or when rolling on overhead wires as trolleys. (See Rail- 
ways, Electric.) 

Plow, Electric A plow driven by an electric 

motor placed either on a wagon to which the plow is attached, 



WORDS, TERMS AND PHRASES. 475 

or by a stationary electro motor, by the aid of cords or other 
flexible belts. 

One of the first practical applications of the electric trans- 
mission of energy was for the operation of a plow, driven 
electrically, by an electric current generated at some distance, 
and transmitted to the field by suitable conductors. 

PliicRer Tubes. — (See Tubes, Plucker.) 

Plug, Infinity (See Infinity Plug.) 

Plumbago. — An allotropic modification of carbon. 

Plumbago, the material commonly known as black lead, is 
the same as graphite. Powdered plumbago is employed in 
electrotyping processes for rendering non-conducting surfaces 
electrically conducting. For this purpose powdered plumbago 
is dusted on the surfaces which thus acquire the power of re- 
ceiving a metallic lustre by friction. Stove polishes are 
formed of mixtures of plumbago and other cheaper materials. 
(See Graphite.) 

Strictly speaking the term graphite is properly applied to 
such varieties of plumbago as are suitable for direct use for 
writing purposes as in lead pencils. 

Plunge Battery.— (See Battery, Plunge.) 

Pneumatic Perforator. — (See Perforator, Pneumatic.) 

Pneumatic Signals, Electro —(See 

Signals, Electro-Pneumatic.) 

Poggendorff's Voltaic Cell.— (See Cell, Voltaic.) 

Points, Electric Action of The effect of points 

placed on an insulated, charged conductor, is to slowly dis- 
charge the conductor by electric convection. (See Convection, 
Electric.) 

The cause of this action is the increased density of a charge 
on the surface of a conductor in the neighborhood of points. 
(See Charge, Distribution of.) 



476 A DICTIONARY OF ELECTRICAL 

Points or Rhumbs, of Compass.— The thirty -two 
points into which a compass card is divided. 

Sixteen of these points are shown in Fig. 310. The position 
of the remaining will be readily seen by an inspection of the 
figures. 

These points are as follows : 

1. North. 

2. N. by E. 

3. N. N. E. 

4. N. E. by N. 

5. N. E. 

6. N. E. by E. 

7. E. N. E. 

8. E. by N. 

9. East. 

10. E. by S. 

11. E. S. E. 

12. S. E. by E. 

13. S. E. 

14. S. E. by S. 

15. S. S. E. 

16. S. by E. 

Boxing the Compass, consists in naming all these points con- 
secutively from any one of them. 

The direction in which the ship is sailing is determined by 
means of a point fixed on the inside of the compass box, 
directly in the line of the vessel's bow. 

Points on Lightning Rod.— Points of inoxidizable 
material, placed on lightning rods, to effect the quiet discharge 
of a cloud by convection streams. (See Lightning Rods. 
Convection, Electric.) 

Polarity, IMamagnetic — A polarity, the re- 
verse of ordinary magnetic polarity, assumed by Faraday to 
explain the phenomena of diamagnetism. (See Diamagnet- 
ism.) 



17. 


South. 


13. 


S. by W. 


19. 


S. S. W. 


20. 


S. W. by S. 


21. 


S. W. 


22. 


S. W. W. 


23. 


W. S. W. 


24. 


W. by S. 


25. 


West. 


26. 


W. by N. 


27. 


W. N. W. 


28. 


N. W. by W. 


29. 


N. W. 


30. 


N. W. by N. 


31. 


N. N. W. 


32. 


N. bv W. 



WORDS, TERMS AND PHRASES. 



477 



Faraday assumed that diamagnetic substances, when brought 
into a magnetic field, such, for example, as north, acquired 
north magnetism in those parts that were nearest the north 
pole, instead of south magnetism as with ordinary magnetic 
substances. The north pole thus obtained, would, he thought, 
explain the apparent repul- 
sion of a slender rod of any 
diamagnetic material, deli- 
cately suspended in a strong 
magnetic field, and cause it 
to point equatorially, or with 
the lines of force passing 
through its least dimen- 
sions. This supposition was 
subsequently abandoned by 
Faraday. It has recently 
been revived by Tyndall. 
(See Diamagnetic.) 

Polarity, magnetic 

The polarity acquired by a magnetizable substance 

when brought into a magnetic field. 

The direction of magnetic polarity, acquired by a substance 
when brought into a magnetic field, depends on the direction in 
which the lines of magnetic force pass through it. Where 
these lines enter the substance a south pole is produced, and 
where they pass out, a north pole is produced. The axis of 
magnetization lies in the direction of the lines of force as they 
pass through the body, and the intensity of magnetization, 
depends on the number of these lines of force. 

The cause of magnetic polarity is not definitely known. 
Hughes's hypothesis attributes it to a property inherent in all 
matter. Ampere attributes it to closed electric circuits in 
the ultimate particles. Whatever its cause, it is invariably 
manifested by a magnetic field, the lines of force of which are 
assumed to have the direction already mentioned. 




Fig. 810. 



478 A DICTIONARY OF ELECTRICAL 

Polarization of Dielectric. — A molecular strain pro- 
duced in the dielectric of a Leyden jar, by the attraction of the 
electricities on its opposite faces, or by electrostatic stress. 
(See Dielectric Strain.) 

The polarization of the glass of a Leyden jar, and the ac- 
companying strain, are seen by the frequent piercing of the 
glass, and by the residual charge of the jar. (See Charge, 
Residual.) 

Polarization of Electrolyte. — The formation of mole- 
cular groups or chains, in which the poles of all the molecules 
of any chain are turned in the same direction, viz. , with their 
positive poles facing the negative plate, and their negative 
poles facing the positive plate. (See Cell, Voltaic. Grothuss , 
Hypothesis.) 

Polarization of Xerves.— (See Electrotonus.) 

Polarization of Voltaic Cell.— The collection of a 
gas, generally hydrogen, on the surface of the negative elo^ 
ment of a voltaic cell. 

The collection of a positive substance like hydrogen on the 
negative element or plate of a voltaic cell, sets up a counter 
electromotive force, which tends to produce a current in the 
opposite direction to that produced by the cell, and thus to 
decrease the normal current of the cell. (See Counter Elec- 
tromotive Force. ) 

The causes of the decrease of the normal current of a vol- 
taic cell by its polarization, are as follows : 

(1) The Increased Resistance of the cell owing to the bubbles 
of gas, which form part of the circuit. 

(2) The Counter Electromotive force, produced by the film 
of gas on the negative plate. 

There are three ways in which the ill effects of this polariz- 
ation can be avoided. These are : 

(1) Mechanical. — The negative plate is furnished with a 
roughened surface which enables the bubbles of gas to escape 



WORDS, TERMS AND PHRASES. 479 

from the points on such surface ; or, a stream of gas, or air, 
is blown through the liquid against the plate to brush the 
bubbles off. 

(2) Chemical. — The surface of the negative plate is sur- 
rounded by some powerful oxydizing substance, such as 
chromic or nitric acid, which is capable of oxidizing the hy- 
drogen, and thus thoroughly removing it from the plate. The 
oxidizing substance may form the entire electrolyte, as is the 
case of the bichromate solution employed in the zinc-carbon 
couple. Generally, however, it has been found preferable to 
employ a separate liquid, like nitric acid to completely sur- 
round the negative plate, and another liquid for the positive 
plate, the two liquids being generally kept from mixing by a 
porous cell, or diaphragm. Such cells are called double fluid 
cells. (See Cell, Voltaic, Double Fluid.) 

(3) Electro Chemical. — This also necessitates a double fluid 
cell. The negative element is immersed in a solution of a 
salt of the same metal as the negative plate. Thus, a copper 
plate, immersed in a solution of copper sulphate, cannot 
be polarized since metallic copper is deposited on its sur- 
face by the action of the hydrogen which tends to be liberated 
there. The constancy of action of a Daniell cell depends on 
a deposition of metallic copper on its copper plate as 
well as on the formation of hydrogen sulphate, and the 
solution of additional copper sulphate. (See Cell, Voltaic, 
DanielVs.) 

Polarized Armature.— (See Armature, Polarized.) 

Polarized Relay.— (See Relay, Polarized.) 

Pole, Antilogous That pole of a pyro-electric 

substance, like tourmaline, which acquires a negative electrifi- 
cation w T hen the temperature is rising, and a positive electrifi- 
cation when it is falling, (See Pyro- Electricity.) 

Pole I'll any it. — A switch or key for changing or re vers- 



480 A DICTIONARY OF ELECTRICAL 

ing the direction oi current produced by any electric source, 
such as a battery. 

The commutator of a Buhmkorff coil is a simple form of 
pole changer. (See Induction Coils.) 

Pole Piece§. — Pieces of soft iron placed at the ends of 
the poles of electro magnets for the purpose of concentrating- 
and directing their magnetic fields. 

Pole Pieces of Dynamos. — Masses of iron connected 
with the poles of the field magnet frames of dynamo-electric 
machines, and shaped to conform to the outline of contour 
of the armature. 

The pole pieces are made in a variety of forms, but in all 
cases are so shaped as to conform to the outline of the space 
in which the armature rotates. 

They are brought as near as possible to the armature so as 
to increase the intensity of the magnetic induction. The in- 
tervening air space should be as thin as possible, but of as 
large an area as convenient. 

The opposite pole pieces should not have their extensions 
brought too near together, as this will permit of serious loss 
through magnetic leakage. The distance between them 
should be as many times the depth of the armature windings 
as possible. (See Magnetic Leakage.) 

Rounded edges are preferable to sharp edges for the same 
reason. 

Poles, Consequent of Magnet.— (See Con- 
sequent Magnet Poles.) 

Poles, False (See False Poles.) 

Poles of Magnetic Intensity. — The earth's magnetic 
poles as determined by means of the needle of oscillation. 

The points of the earth's greatest magnetic intensity. (See 
Inclination Chart.) 

Poles of Verticity, Magnetic. — The earth's magnetic 
poles as determined by means of the dipping needle. 



WORDS, TERMS AND PHRASES. 481 

The points of the north where the angle of dip is 90°. (See 
Inclination Chart.) 

Poles, Telegraphic Wooden or iron uprights on 

which telegraphic or other wires are hung. 

Wooden poles are generally round. 

The terminal pole, or the last pole at each end of the line, 
or where the wires bend at an angle of nearly 90°, is gener- 
ally cut square. 

The holes for the poles must be dug in the true line of the 
wires, and not at an angle to such line. As little ground 
should be disturbed in the digging as possible. Earth borers, 
or modifications of the ordinary ship auger, are generally 
employed for this purpose. When the pole is placed in posi- 
tion the ground should be rammed, or punned around the 
pole. 

In setting the pole, it is generally set at least five feet in 
the ground. In England the poles are planted to a depth of 
about one-fifth of their length. In embankments and loose 
ground, they are planted deeper than in more solid earth. On 
curves, the poles should be inclined a little so as to lean back 
against the lateral strain of the wire, since by the time the 
ground has completely set, the strain of the wire will have 
pulled them into an erect position. 

Care must be taken to so plant the poles on that side of a road 
or railway, that the prevailing winds will blow them off the 
same, should it overturn them. As to location, the top of 
steep cuttings is preferable to the slope. In all exposed posi- 
tions, it is preferable to strengthen the poles by stays attached 
to both sides. 

Where the number of wires is unusually large, heavy 
timber, or in case of its absence, double poles suitably braced 
together, must be employed. In long lines the poles should 
all be numbered in order to afford ease for reference or repair. 

When, even with the best punning, and other precautions, 
the pole is judged to be unable to resist the strain on it, stays 



482 



A DICTIONARY OF ELECTRICAL 



and struts are employed. A stay is used when it is desired to 
remove the pull or tension from the pole ; a strut, when it is 
desired to remove the thrust or pressure. 





Fig. $11. 

The arms or brackets, or the cross pieces that support the 
insulators, should all be placed on the same side of the poles. 
Some common forms of arms or brackets are shown in 
Fig. 311. 

Saddle Brackets should be placed on alternate sides of the 
pole. When the strain on an insulator is too great, on ac- 

^Kb ms* — **> . count of the wire 

going off at a sharp 

angle, a Shackle is 
used. This is a spec- 
ial form of insulator 
which confines the 
Fig. 812. strain to one spot. 

A form of Double Shackle is shown in Fig. 312. The wire 
passes around the recess at B, between the two insulators. 
On curves, or in any situation when there is a probability, in 




WORDS. TERMS AND PHRASES. 



case of the breaking of an insulator, of a wire getting into a 
dangerous position Guards should be employed. 

Guards are of two kinds, viz.: Hoop Guards and Hook 
Guards. A form of hook guard is shown in Fig. 313. 

When wooden poles are employed various preservative 
methods are adopted to protect the wood from decay, which is 
very apt to occur, especially at the line of the pole enters the 
ground. Some of these forms are as follows, viz. : 

(1) Charring and Tarring the ^^^ 
butt end of the pole where it en- /^^^ 
ters the ground, so as to expel the /Y 

sap and destroy injurious plants or // 
animal germs. 

The charred end is then cleansed 
and dipped in a mixture of tar and 
slaked lime. 

(2) Burnetising, or the introduc- 
tion of chloride of zinc into the 
pores of the wood, by placing the 
poles in an open tank filled with a 
solution of this salt. 

(3) Kyanising, or the similar in- 
troduction of corrosive sublimate, ^3" 
or mercuric chloride. Fig ' 313 ' 

(4) Boucherising, or the injection of a solution of copper sul- 
phate, into the pores of the wood. 

(5) Creosoting, or the application of creosote to well -sea- 
soned poles. 

Porous Cells. — Jars of unglazed earthenware, employed 
in double-fluid voltaic cells, to keep the two liquids separated. 

The use of a porous cell necessarily increases the internal 
resistance of the cell, from the decrease it produces in the area 
of cross section of liquid between the two elements. When 
the battery is dismantled, the porous cells should be kept under 
water, otherwise the crystallization of the zinc sulphate or 




484 A DICTIONARY OF ELECTRICAL 

other salt is apt to produce serious exfoliation, or even to 
crumble the porous cell. 

A porous cell is sometimes called a diaphragm. (See Cell, 
Voltaic.) 

Portative Power. — The lifting- power of a mag-net. 
(See Lifting Power of Magnet.) 




Fig. Slh. 

Portrait, Electric A portrait formed on paper by 

the electric volatilization of gold or other metal. 

An electric portrait, is obtained by cutting on a thin card a 
portrait, in the form of a stencil. A sheet of gold leaf is then 
placed on one side of the paper stencil, and a sheet of paper 
on the other side ; sheets of tin foil are then placed on the 
outside, as shown in Fig. 314, and the whole firmTy p'-essed 



WORDS, TERMS AND PHRASES. 485 

together. If now a disruptive discharge is passed through 
from one sheet of tin foil to the other, the gold leaf is vo- 
latilized, and a purplish stain is left on the paper on the 
outlines of the stencilled card, thus forming an electric por- 
trait. 

Positive Electricity. — One of the phases of electrical 
excitement, rather than one of the kinds of electricity. (See 
Negative Electricity.) 

Positive Direction of Lines of Magnetic Force. 
— The direction the lines of magnetic force are assumed to 
take, viz. : out of the north pole of a magnet and into the south 
pole. (See Field, Magnetic. Direction of Lines of Force.) 

Posts, Binding or Binding Screws, — (See 

Binding Posts.) 

Potential, Constant -A potential which remains 

constant under all conditions. 

A machine or other electric source is said to have a con- 
stant potential when it is capable, while in operation, of main- 
taining a constant difference of electric pressure between its 
two terminals. (See Circuit, Constant Potential.) 

Potential, Difference of (See Difference 

of Potential.) 

Potential, Difference of Methods of Meas- 
uring Methods employed for determin- 
ing difference of potential. 

These methods are as follows : 

(1) By the Method of Weighing, that is, by obtaining the 
weight required to overcome the attraction between two op- 
positely charged plates, or oppositely energized coils ; or by 
measuring the repulsion between similarly charged surfaces, 
or similarly energized coils. 

(2) By the use of Electrometers, or apparatus designed for 
measuring differences of potential. (See Electrometers.) 

(8) By the use of Galvanometers. 



486 A DICTIONARY OF ELECTRICAL 

Difference of potential, in the case of currents, may be 
determined from the quantity of electricity which flows per 
second through a given circuit, that is, by the number of 
amperes, just as the pressure of water at any point in the side 
of a containing vessel can be determined by the quantity of 
water that flows per second. Difference of potential in the 
case of currents, therefore, may be measured by any galvano- 
meter which measures the current directly in amperes, and 
knowing the resistance of the circuit. 

Potential, Electric The power of doing 

electric work. 

Electric level. 

Electric potential can be best understood by comparison 
with the case of a liquid such as water. 

The ability of a water supply or source to do work depends: 

(1) On the Quantity of Water. 

(2) On the Level of the Water, as compared with some other 
level, or, in other words on the difference between the two 
levels. 

In a like manner the ability of electricity to do work de- 
pends : 

(1) On the Quantity of Electricity. 

(2) On the Electric Potential at the place where the elec- 
ricity is produced, as compared with that at some other place, 

r, in other words on the Difference of Potential. 

In the case of water flowing through a pipe, the quantity 
which passes in a given time is the same at any cross section of 
the pipe. 

In the case of electricity, the quantity of electricity flowing 
through any conductor, or part of a circuit, is the same at any 
cross section. A galvanometer introduced into a break in any 
part of the conductor would show the same strength of 
current. 

But, though the quantity of water which passes is the same 
at any cross section of a pipe, the pressure per square inch is 



WORDS, TERMS AND PHRASES. 



487 



not the same, even in the case of a horizontal pipe of the same 
diameter throughout, but becomes less, or suffers a loss of 
head, or difference of pressure, at any two points along the 
pipe, that causes the flow between these two points against 
the resistance of the pipe. 

So too, in the case of a conductor carrying an electric cur- 
rent, though the quantity of electricity that passes is the same 
at all cross sections, the electric pressure or potential is by no 
means the same at all points in the conductor, but suffers a 
loss of electric head or level in the direction in which the 
electricity is flowing. It is this loss of electric head or level, or 
difference of electric potential, that causes the electricity 
to flow against the resistance of the conductor. 



a 

a ^6 



d_ 


z: 


e 




f '-- 




Fig. 815. 

These analogies can be best shown by the following illus- 
tration : 

In Fig. 315, a reservoir, or source of water, at C, communi- 
cates with the horizontal pipe A B, furnished with open 
vertical tubes at a, b, c, d, e, f, g, and B. If the outlet at B is 
closed, the level of the water in the communicating vessels 
is the same as at the source ; but if the liquid escape freely 
from B, the level of the water in the branch pipes, will be 
found on the inclined dotted line or at a', b', c' , d', e' , f, a 1 , 
or on the hydraulic gradient. 



488 



A DICTIONARY OF ELECTRICAL 



The pressure per square inch, at any cross section of the 
horizontal pipe, which is measured by the height of the liquid 
in the vertical pipe at that point, decreases in the direction in 
which the liquid is flowing. The force that urges the liquid 
through the pipe between any two points, may be called the 
liquid-motive force (Fleming) and is measured by the differ- 
ence of pressure between these points. 

In Fig. 316, the dynamo electric machine at D, has its nega- 
tive pole grounded, and its positive pole connected to a long 
lead, A B, the postive end of which is also grounded. A fall 
of potential, represented by the inclined dotted line, occurs be- 
tween A and B, in the direction in which the electricity isflow- 
in 9> n fv^a> 




-x: 



*-«.• 



0" [El 

Fig. 316. I — I 

The dynamo electric machine may be regarded as a pump 
that is raising the electricity from a lower to a higher level, 
and passing it through the lead A B. The electric pressure or 
potential producing the flow is greatest near the dynamo and 
least at the further end, the differences at the points a, b, c, 
d, e, f, and g, being represented by the vertical lines a a', b b', 
c c', d d', e e', ff, and g g'. 

The electricity flows between any two points as a, and b, 
in the conductor A B, in virtue of the difference of electric 
pressure or potential between these two parts, or the differ- 
ence between a a', and b b'. 

Differences of potential must be distinguished from differ- 



WORDS, TERMS AND PHRASES. 489 

ences in electric charge, or electrostatic density. If two con- 
ductors at different potentials are connected by a conductor, 
a current will flow through this conductor. When their 
potential is the same no current flows. The density of a 
charge is the quantity of electricity per unit of area. 

The electric potential is the same at all points of an insulated 
charged conductor ; the density is different at different points, 
except in the case of a sphere. The potential, however, is the 
same, since no current flows, or the charge does not redistribute 
itself. The density on an insulated, isolated sphere is uniform 
over all parts of the surface, and its potential is the same at all 
points. If now the sphere be approached to another body, its 
density will vary at different parts of its surface, and while 
the charge is redistributing itself so as to produce these differ- 
ences in density the potential will vary. As soon, however, as 
this redistribution is effected and no further current exists, the 
potential is the same over all parts, though the density differs 
at different points. 

Potential, Electrostatic The power of doing 

work possessed by a unit quantity of positive electricity charged 
on an insulated body. 

The electric potential of any point may also be defined as 
being equal to the work required to be exerted on a unit of 
positive electricity in bringing it to that point from zero poten- 
tial, i. e., from an infinite distance. 

Potential Energy. — Energy possessing the power or po- 
tency of doing work, but not actually performing such work. 
(See Energy, Potential.) 

Potential, Fall of (See Potential, Electric.) 

Potential, Magnetic The amount of work re- 
quired to bring up a unit north-seeking magnetic pole from an 
infinite distance to another unit north-seeking magnetic pole. 

Potential of Conductor, Methods of Varying 



490 A DICTIONARY OF ELECTRICAL 



— The potential of a conductor may be varied 

in the following ways : 

(1) By varying its electric charge. 

(2) By varying its shape without altering its charge. 

(3) By varying its position as regards neighboring bodies. 
This resembles the case of a gas whose tension or pressure 

may be varied as follows, viz. : 

(1) By varying the quantity of gas. 

(2) By varying the size of the gas holder in which it is kept, 
and, 

(3) By varying the temperature. 
Difference of potential, therefore corresponds, 

(1) With difference of level in liquids. 

(2) "With difference of pressure in gases. 

(3) With difference of temperature in heat. (Ayrton.) 
Potential, Zero An arbitrary level from which 

electric potentials are measured. 

As we measure the heights of mountains from the arbitrary 
mean level of the sea so we measure electric levels from the 
arbitrary level of the potential of the earth. 

The true zero potential would be situated at a point infinitely 
distant from any electrified body. 

Potentiometer. — An apparatus for the galvanometric 
measurement of electro-motive forces, or differences of poten- 
tial by a zero method. (See Null, or Zero Methods.) 

In the potentiometer the difference of potential to be 
measured is balanced, or opposed, by a known difference of 
potential, and the equality of the balance is determined by the 
failure of one or more galvanometers, placed in shunt circuits, 
to show any movement of their needles. 

The principle of operation of the potentiometer will be 
understood from an inspection of Fig. 317. A secondary bat- 
tery S, has its terminals connected to the ends of a uniform 
wire A B, of high resistance called the Potentiometer 
Wire. There will therefore occur a regular drop or fall of 



WORDS, TERMS AND PHRASES. 491 

potential along this wire, which, since the wire is uniform, will 
be equal per unit of length. This drop of potential can be 
shown by connecting the terminals of a delicate high resis- 
tance galvanometer to different parts of the wire, when the 
deflection of the needle will be proportional to the drop of 
potential between the two points of the wire touched. If 
now the terminals of a Standard Cell be inserted in the 
circuit of the galvanometer, so as to oppose the current taken 
from the potentiometer wire, and the contacts of the 
potentiometer wire be slid along it until no deflection of 
the galvanometer needle is produced, the drop of potential 
between these two points on the potentiometer wire will be 
equal to the difference of poten- 
tial of the standard cell. (See 
Standard Cell.) 

Suppose now it be desired to 
measure the difference of poten- 
tial between two points a and 6, 
on the wire C, through which a 
current is flowing. Connect the 
points b and d, and a and c, as Ftg ' 317 ' 

shown, with the delicate high resistance galvanometer G, in 
either of them. Now slide c towards d, until the needle of 
G shows no deflection. The potential between a and b, is 
then equal to that between c and d. 

Potentiometer Wire.— The wire of a potentiometer 
which has been calibrated for its drop of potential. (See 
Potentiometer.) 

Power. — Rate of doing work. 

Mechanical power is generally measured in horse power, 
which is equal to work done at the rate of 550 foot-pounds 
per second. 

The C. G. S. Unit of Power is one Erg per Second. 

The practical unit of power is the Watt, or 10,000,000 ergs 
per second. 

1 Watt = 7 £ F H. P. 




492 



A DICTIONARY OF ELECTRICAL 



Power, Absorptive 
Power, Stray 



-(See Absorptive Power.) 



-(See Stray Power.) 



Power, Thermo-EIectric 



-A number which, 



when, multiplied by the difference of temperature of a ther- 
mo-electric couple, will give the difference of potential 
thereby generated in micro-volts. (See Diagram, Thermo- 
EIectric.) 

Power, Unit§ of — 
measurement of power. 

The following table of 
taken from Herimr's worl 



Units of Work, and of Power 
on Dynamo Electric Machines : 
Work 

erg = 1. dyne-centimetre. 

" = .0000001 joule. 

gram-centimetre = 981.00 ergs. 

" = . 00001 kilogram-metre. 

= 1937.5 ergs. 
\ = 10,000,000 ergs. 
= .737324 foot-pound. 



foot-grain _. 

joule, or .- 

volt-coulomb, or 

watt during every sec- 
ond, or. 

1 volt-ampere d u r i n g 
every second 



1 foot-pound 



.101937 kilogram-metre. 

/= .0013592 metric horse power for 

one second. 
= .0013406 horse power for one 

second. 
= .0009551 pound-Fah., heat unit. 
= .0005306 pound-Centig., heat 

unit. 
= .0002407 kilogr. - Centig. heat 

unit. 
= .0002778 watt-hour. 
= 13562600 ergs. 
= 1.35626 joules. 



WORDS, TERMS AND PHRASES. 493 

1 foot-pound = .13825 kilogram-metre. 

" = .0018434 metric horse-power for 

one second. 

" =.00181818 horse-power for one 

second. 

" = .0012953 pound-Fah., heat unit, 

= .0007196 pound - Centig., heat 

unit. 

=.0003264 kilogr. -Centig., heat 

unit. 

= . 0003767 watt-hour. 

1 kilogram-metre _ . = 98100000 ergs. 

= 9.81000 joules. 

= 7.23314 foot-pounds. 

" = .01333 metric horse-power for 

one second. 

" =.013151 horse - power for one 

second. 

= .009369 pound-Fah. , heat unit, 

" = .005205 pound-Centig., heat unit. 

= . 002361 kilogr. -Centig. heat unit. 

= . 002725 watt-hour. 

1 watt-hour = 3600. joules. 

= 2654.4 foot-pounds. 

- . . = 366. 97 kilogram-metres. 

= 3.4383 pound-Fah., heat units. 

" .= 1.9102 pound-Centig., heat units. 

" = .8664 kilogr. -Centig., heat units. 

" -.. = .0013592 metric horse - power- 
hour. 

" = .0013406 horse-power-hour. 

1 metric horse-power-hour = 2648700 joules. 

= 1952940 foot-pounds. 
" = 270000 kilogram-metres. 

" = 2529.7 pound-Fah., heat units. 



494 A DICTIONARY OF ELECTRICAL 

1 metric horse-power-hour = 1405.4 pound-Centig., heat units. 
= 637. 5 kilogr. -Centig. , heat units. 
" = 735.75 watt-hours. 

" = .98634 horse-power-hour. 

1 horse-power-hour = 2685400 joules. 

= 1980000. foot-pounds. 

" =273740 kilogram-metres. 

" = 2564.8 pound-Fan., heat units. 

" = 1424.9 pound-Centig., heat units. 

" = 646.31 kilogr. -Centig. , heat units. 

= 745.941 watt-hours. 

" =1.01385 metric horse - power - 

hour. 
Heat. 

1 gram -Centigrade = .001 kilogram-Centigrade. 

1 pound-Fahrenheit = 1047.03 joules. 

« ' = 772 foot-pounds. 

" ...._= 106.731 kilogram-metres. 

" = .55556 pound-Centigrade. 

" = . 25200 kilogram-Centigrade. 

" = . 29084 watt-hour. 

" = .0003953 metric horse- power - 

hour. 

" = .0003899 horse-power-hour. 

1 pound-Centigrade = 1884.66 joules. 

= 1389.6 foot-pounds. 

" = 192.116 kilogram-metres. 

" = 1.8000 pound-Fahrenheit. 

" = .4536 kilogram-Centigrade. 

" = .52352 watt-hour. 

" =.0007115 metric horse -power- 

hour. 

" = .0007018 horse-power-hour. 

1 kilogram-Centigrade = 4154.95 joules. 

« = 3063.5 foot-pounds. 



WORDS, TERMS AND PHRASES. 



495 



1 kilogram-Centigrade. 



1 erg per second 

1 watt, or 

1 volt-ampere, or 

1 joule per second, or 

1 volt-coulomb per second 



1 foot-pound per min. 



1 kilogram 



metre per min 



1 metric horse-power . 

or 

1 French horse-power 

or. 



= 423.54 kilogram-meters. 

= 3.9683 pound-Fahrenheit. 

= 2.2046 pound-Centigrade. 

= 1.1542 watt-hours. 

= .001569 metric horse - power - 

hour. 
= .0015472 horse-power-hour. 

Power, 

= .0000001 watt. 

= 10000000. ergs per second. 

= 44.2394 foot-pounds per min. 

= 6.11622 kilogram - metres per 

min. 
= .0573048 lb. -Fan., heat unit per 

min. 
= .0318360 lb.-Cent., heat unit per 

min. 
= .0144402 klgr.-Cent. heat unit 

per mm. 
= .0013592 metric horse-power. 
= .0013406 horse-power. 
= 226043 ergs per second. 
= .0226043 watt. 

= . 13825 kilogram-metre per min. 
= .00003072 metric horse-power. 
= .000030303 horse-power. 
= 1635000. ergs per second. 
= .163500 watt. 

= 7.23314 foot-pounds per min. 
= .0002222 metric horse-power. 
= .0002192 horse-power. 
= 735.75 x 10 7 ergs per second. 
= 735.750 watts. 
= 32549.0 foot-pounds per min. 
= 4500 kilogram-metres per min. 



496 A DICTIONARY OF ELECTRICAL 

1 cheval-vapeur, or ... ... = 42.162 lb.-Fah., heat units per 

min. 

1 force de cheval, or = 23.423 lb. -Cent, heat units per 

min. 

1 Pferdekraft = 10.625 klg.-Cent., heat units per 

min. 

" = .98634 horse-power heat units 

per min. 

1 horse-power = 745.94 x 10 7 ergs per second. 

= 745.941 watts. 

" = 33000 foot-pounds per min. 

" .„_„ =4562.33 kilogram - metres per 

min. 

" =42.746 lb.-Fah., heat units per 

min. 

« =23.748 lb. -Cent., heat units per 

min. 

" = 10. 772 klg. -Cent. , heat units per 

min. 

" = 1.01385 metric horse-power. 

1 lb. Fah., heat unit per 

min = 17.45 x 10 7 ergs per second. 

" = 17.4505 watts. 

" = .23718 metric horse-power. 

" = .023394 horse-power. 

1 lb. Cent., heat unit per 

min = 31.41 x 10 7 ergs per second. 

" = 31.4109 watts. 

" = .04269 metric horse-power. 

" = .042109 horse-power. 

1 klgr. -Cent. , heat unit per 

min = 69.25 x 10 7 ergs per second. 

" = 69.249 watts. 

" = .09412 metric horse-power. 

*' - .092835 horse-power. 

(Hering.) 



WORDS, TERMS AND PHRASES. 497 

Practical Units. — (See Units, Practical) 

Primary Battery.— (See Battery, Primary. ) 

Prime Conductor. — The positive conductor of a frac- 
tional electric, or electrostatic machine. (See Machine, Elec- 
tric, Fractional.) 

Prime Motor.— (See Motor, Prime.) 

Probe, Electric Metallic conductors, inserted 

in the body of a patient, to ascertain the exact position of a 
bullet or other metallic body. 

The conductors are placed parallel, and are separated at the 
extremity of the probe by any suitable insulating- material. 
On contact with the metallic substance, an electric bell is 
rung- by the closing of the circuit, or the same thing is more 
readily detected by the deflection of the needle of a galvano- 
meter, or by a telephone placed in the circuit. 

Process, Electrotype (See Electrotype Process.) 

Processes of Carbonization.— (See Carbonization, 
Processes of. ) 

Prony-Brake.— (See Brake, Prony.) 

Proof-Plane. — A small insulated conductor employed to 
take test charges from the surface of an insulated, charged 
conductor. 

The proof-plane is used in connection with some forms of 
electrometer. — (See Balance, Torsion, Coulomb's.) 

Proof-Plane, Magnetic A small 

coil of wire placed in the circuit of a delicate galvanometer, 
and used for the purpose of exploring a magnetic field. 

When the coil is suddenly inverted in a magnetic field, if a 
long coil galvanometer provided with a heavy needle is used, 
the number of lines of force which pass through the area of 
cross section of the coil, will be proportional to the sine of 
half the angle of the first swing of the needle. 



498 A DICTIONARY OF ELECTRICAL 

Proportionate Arms of Electric Bridge.— A term 
applied to two of the arms of an electric bridge or balance. 
(See Balance, Whealstone's Electric, Box Form of.) 

Prostration, Electric (See Sun Stroke, Elec- 
tric.) 

Protection, Electric of Houses, Ship* and 

Buildings Generally. (See Lightning Rods.) 
Protection, Electric of Metals.— (See 

Metals, Electric Protection of.) 

Protector, Lightning (See Lightning Ar- 
rester.) 

Protector, Vacuum Lightning A protec- 
tor consisting of a glass vessel in which the line wires and 
an earth wire are fused, and in which a partial vacuum is 
maintained. 

Vacuum protectors are employed on the lines of submarine 
cables, or underground lines, in order to protect them from 
lightning discharges. 

A discharge of high potential passes more readily through 
this partial vacuum to the ground ohan through the line 
wires. 

Protoplasm, Effects of Electric Currents on 

— Contractions observed in all protoplasm on 



the passage of an electric current through it. 

Protoplasm, the basis of plant and animal life, or the jelly 
like matter that fills all organic cells, whatever may be the 
origin of such cells, suffers contraction when traversed by an 
electric current. 

An increased activity of the movements of the amoeba is 
occasioned by slight shocks from an induction coil ; stronger 
discharges produce tetanic contractions, with, in some cases, 
expulsion of food or even of the nucleus. A uniform 
strength of current produces contraction and imperfect 
tetanus. 



WORDS, TERMS AND PHRASES. 



499 



Pump, Mechanical Air- 



— A mechanical device 



for exhausting or removing the air from any vessel. 

An excellent form of air pump is shown in Fig. 318, which 
is a drawing of Bianchi's pump. 

Three valves, all opening upwards, are placed at the top 
and bottom of the cylinder, and in the piston, respectively. 
These valves are mechanically opened and closed at the 
proper moment by the movements of the piston, i. e., their 
action is automatic. This enables 



tained than when the valves open 
and close by the tension of the 
air. 

Mechanical pumps are unable 
to readily produce the high vacua 
employed in most electric lamps. 
Mercury pumps are employed for 
this purpose. 

Pumps, Mercurial Air 

— Devices for obtaining 




Fig. 318. 



high vacua by the use of mercury. 

Mercury pumps are, in general, 

of two types of construction, viz. : 

(1) The Geissler Pump. 

(2) The Sprengel Pump. 
In the Geissler Mercury Pump, 

Fig. 319, a vacuum is obtained by 
means of the Torricellian vacuum produced m a large glass 
bulb that forms the upper extremity of a barometric column. 
(See Barometric Column.) The lower end of this tube or 
column is connected with a reservoir of mercury by means of 
a flexible rubber tube. To fill the bulb with mercury the 
reservoir is raised above its level, i. e., above thirty inches, 
the air it contains being allowed to escape through an open- 
ing governed by a stop-cock. The vessel to be exhausted is 



500 



A DICTIONARY OF ELECTRICAL 




Fig. 319. 



WORDS, TERMS AlJD PHRASES. 



501 



connected with the bulb, and by means of a two-way exhaus- 
tion cock, communication can be made with the bulb, when it 
contains a Torricellian 
vacuum, and shut off 
from it while its air is 
being expelled. 

In actual practice the 
mercury is mechanic- 
ally pumped into the 
barometric column, and 
the valves are opened 
either by hand, or, au- 
tomatically by suitable 
mechanism, or by elec- 
trical means. 

In the Sprengel Mer- 
cury Pump, Fig. 320, a 
vacuum is obtained by 
means of the fall of a 
stream of mercury in a 
vertical tube of compar- 
atively fine bore, which 
dips below a mercury 
level. The fall of a mer- 
cury stream causes the 
exhaustion of a reser- 
voir connected with the 
vertical tube, by the me- 
chanical action of the 
mercury in entangling 
babbles of air. These 
bubbles are largest at 
the beginning of the Fig. 320. 

exhaustion, but become smaller and smaller near the end, 
until, at last, the characteristic metallic click of mercury or 




502 



A DICTIONARY OF ELECTRICAL 




other liquid falling in a good vacuum is heard. The exhaust- 
ion may be considered as completed when the bubbles entirely 
disappear from tue column. 

The Sprengel pump produces a better vacuum than the 
Geissler pump, but is slower in its action. 

In actual practice, the mercury that has fallen through the 
tube is again raised to the reservoir connected to the drop tube 
by the action of a mechanical pump. 

Punning of Telegraph Poles.— Ramming or packing 
the earth around the base of a telegraph 
pole for the purpose of more securely 
fixing it in the ground. 

Push Button. — (See Button, Push.) 

Pyro Electricity.— Electricity de- 
veloped in certain crystalline bodies by 
heating or cooling them. 

Tourmaline possesses this property in 
a marked degree. When a crystal of 
tourmaline is heated or cooled, it acquires 
opposite electrifications at opposite ends 
or poles. 

In the crystal of tourmaline shown in 
Fig. 321, the end A, called the analogous 
pole, acquires a positive electrification, and the end B, called 
the antilogous pole, a negative electrification, while the tem- 
perature of the crystal is rising. While cooling the opposite 
electrifications are produced. 

A heated crystal of tourmaline, suspended by a fibre, is at- 
tracted or repelled by an electrified body or by a second heated 
tourmaline, in the same manner as an electrified body. 

Many ciystalline bodies possess similar properties. Among 
these are the ore of zinc known as electric calamine or the 
silicate of zinc, boracite, quartz, tartrate of potash, sulphate 
of quinine, etc. 



^ 




A 
Fig. , 



WORDS, TERMS AND PHRASES. 



503 



Pyromagnetic Motor.— A motor driven by the attrao 
tion of magnet poles on a movable core of iron unequally 
heated. 




Fig. sn. 
The intensity of magnetization of iron decreases with an in- 
crease of temperature, iron losing most of its magnetization at 



504 



A DICTIONARY OF ELECTRICAL 



a red heat. A disc of iron, placed between the poles of a 
magnet so as to be capable of rotation, will rotate if heated 
at a part nearer one pole than the other, since it becomes less 
powerfully magnetized at the heated part. 




Fig. 323. 
In the form of pyromagnetic motor devised by Edison, and 
shown in Fig. 322, in elevation, and in Fig. 323, in vertical sec- 



WORDS, TERMS AND PHRASES. 



505 



tion, the disc of iron is replaced by a series of small iron tubes, 
or divided annular 
spaces, heated by the 
products of combustion 
from a fire placed be- 
neath them. In order 
to render this heating 
local, a flat screen is 
placed dissymetrically 
across the top to pre- 
vent the passage of air 
through the portion of 
the iron tubes so 
screened. The air is 
supplied to the furnace 
by passing down from 
above through the tubes 
so screened. This is 
shown in the drawings, 
the direction of the 
heating and the cooling 
air currents being in- 
dicated by the arrows. 
The supply of air from 
above thus insures the 
more rapid cooling of 
the screened portion of 
the tubes. 

Pyromagnetic 
Generator or Dy- 
namo. — An apparatus 
for producing electric- 
ity directly from the 
burning of fuel. Fig. s%. 

The operation of the generator is dependent on the fact, 




506 A DICTIONARY OF ELECTRICAL 

that any variation in the number of lines of magnetic force 
that pass through a conductor, will develop differences of 
electric potential therein. Such variations may be effected 
either by varying the position of the conductor as regards 
the magnetic field, or by varying the intensity of the magnetic 
field itself. The latter method qf generating differences of 
potential is utilized in the pyromagnetic generator, and is 
effected in it by varying the magnetization of rolls of thin 
iron by the action of heat. 

A form of pyromagnetic generator devised by Edison is 
shown in Figs. 324 and 325. 

Eight electro-magnets are provided each with an armature, 
consisting of a roll of corrugated iron. Each of these arma- 
tures is provided with a coil of insulated wire wound on it 
and protected by asbestos paper. These armatures pass 
through two iron discs as shown. The armature coils are con- 
nected in series in closed circuit, the wires from the coils being 
connected with metallic brushes that rest on a commutator, 
supported on a vertical axis. A pair of metallic rings is 
provided above the commutator to carry off the current gene- 
rated. The vertical axis is provided below with a semi- 
circular screen called a guard plate which rotates with the 
axis and cuts off or screens one-half the iron armatures from 
the heated air. 

When the axis is rotated, the differences in the magnetiza- 
tion of the armatures, when hot and cold, develop differences 
in electromotive force which result in the production of an 
electric current. 

Pyrometer. — An instrument for determining tempera- 
tures higher than those that can be readily measured by ther- 
mometers. 

Pyrometers are operated in a variety of ways. A common 
method is by the expansion of a metal rod. 

Pyrometer, Siemen§> Electric An 



WORDS, TERMS AND PHRASES. 



507 



apparatus for the determination of temperature by the meas- 
urement of the electric resistance of a platinum wire exposed 
to the heat whose temperature is to be measured. 




Fig. 325. 

The platinum wire is coiled on a cylinder of fire-clay, so 
that its separate convolutions do not touch one another. It is 
protected by a platinum shield, and is exposed to the tempera- 
ture to be measured while inside a platinum tube. 

The resistance of the platinum coil at 0° C. having been 



508 A DICTIONARY OF ELECTRICAL 

accurately ascertained, the temperature to which it has been 
exposed can be calculated from the change in its resistance 
when exposed to the unknown temperature. 

Pyrometer, Siemens' Water A pyrometer 

employed for determining the temperature of a furnace, or 
other intense source of heat, by calorimetric methods, i. e., by 
the increase in the temperature of a known weight of water, 
into which a metal cylinder of a given weight has been put, 
after being exposed for a given time to the source of heat 
to be measured. 

When copper cylinders are employed, the instrument pos- 
sesses a range of temperature of 1800° F.; when a platinum 
cylinder is used, it has a range of 2700° F. 

Quadrant Electroscope, Henley's (See 

Electroscope, Quadrant, Henley's.) 

Quadrant Electrometer.— (See Electrometer, Quad- 
rant.) 

Quadruplex Telegraphy.— A system of telegraphy by 
means of which four messages can be simultaneously trans- 
mitted over a single wire, two in one direction, and two in the 
opposite direction. — (See Telegraphy, Quadruplex.) 

Qualitative Analysis. — (See Analysis.) 

Quality of Disruptive Discharge, How Affected. 

— The appearance of the disruptive discharge as affected by a 
variety of circumstances. — (See Discharge, Disruptive.) 

Quality or Timbre of Sound.— That peculiarity of a 
musical note which enables us to distinguish it from another 
musical note of the same tone or pitch, and of the same in- 
tensity or loudness, but sounded on another instrument. 

The middle C, for example of a pianoforte, is readily dis- 
tinguishable from the same note on a flute, or on a violin ; that 
is to say, its quality is different. The differences in the quality 
of musical sounds are caused by the admixture of additional 



WORDS, TERMS AND PHRASES. 509 

sounds called overtones which are always associated with any 
musical sound. 

Briefly, nearly all so-called simple musical sounds, are in 
reality chords or assemblages of a number of different musical 
sounds. 

One of these notes is far louder than all the others and is 
called the fundamental tone or note, and is what is recognized 
by the ear as the note proper. The overtones are too feeble 
to be heard very distinctly, but their presence gives to the note 
proper its own peculiar quality. In the case of a note sounded 
on the flute, these overtones are different either in number 
or in their relative intensities from the same note sounded on 
another instrument. Their fundamental tones, however, are 
the same. 

The peculiarities which enable us to distinguish the voice 
of one speaker or singer from another are due to the presence 
of these overtones. The over-tones must be correctly repro- 
duced by the diaphragm of the telephone, or phonograph, 
graphophone, or gramophone, if the articulate speech is to be 
correctly reproduced with all its characteristic peculiarities. 

Quantitative Analysis — (See Analysis.) 

Quantity, Arrangement of Voltaic Cell§ for 

— A term, now generally in disuse, to indicate the grouping of 
voltaic cells, technically known as parallel or multiple-arc. 

The arrangement or coupling of a number of voltaic cells 
in multiple-arc being an arrangement that reduces the internal 
resistance of the battery, and thus permits a greater current, 
or quantity of electricity to pass ; hence the origin of the term. 

Quantity, Unit of Eleetric A definite amount 

or quantity of electricity called the coulomb. — (See Coulomb.) 

Although the exact nature of electricity is unknown, yet 
it acts like a fluid (a liquid or gas) and can be accurately 
measured as to quantity. 

A current of one ampere, for example, is a current in which 
one coulomb of electricity passes in every second. 



510 A DICTIONARY OF ELECTRICAL 

A condenser of the capacity of one farad is large enough 
to hold one coulomb of electricity if forced into the vessel 
under an electro-motive force of one volt.— (See Capacity. 
Farad. Volt.) 

Quiet Discharge.— (See Discharge, Convective.) 

Radiant Energy. — Energy transferred to, or charged on, 
the universal ether. 
Radiant energy is of two forms, viz. : 

(1) Obscure Radiation, or Heat. 

(2) Luminous Radiation, or Light. 

Radiant Matter.— (See Matter, Radiant.) 

Radiophony. — The production of sound by a body cap- 
able of absorbing radiant energy, when an intermittent beam 
of light or heat falls on it. 

The action of radiant energy, when absorbed by matter, is 
to cause its expansion by the consequent increase of temper- 
ature. This occurs even when the body is but momentarily 
exposed to a flash of light, but the instantaneous expansion, 
thus produced, immediately dies away, and by itself is indis- 
tinguishable. If, however, a sufficiently rapid succession of 
such flashes fall on the body, the instantaneous expansions 
and contractions produce an appreciable musical note. 

The sounds so produced have been utilized by Bell and 
Tainter in the construction of the Photophone. (See Photo- 
phone.) 

Radiation. — The transference of energy by means of 
ether waves. 

Radicals. — Unsaturated atoms or molecules, in which 
one or more of the bonds are left open or free. 

Radicals are either Simple or Compound. 

The radical may be regarded as the basis to which other 
elements may be added, or as the nucleus around which they 
may be grouped. 



WORDS, TERMS AND PHRASES. 511 

Thus H 2 forms a complete chemical molecule, because 
the bonds of all its constituent atoms are saturated, thus 
H — O — H. But H — O — , or hydroxyl, is a radical, because 
its oxygen atom possesses one unsaturated or free bond. By- 
combining with the radical, (N0 2 ), it forms nitric acid, thus 
H — O — (NO,) = HN0 8 . 

During electrolysis, the molecule of the electrolyte is de- 
composed into two simple or compound radicals, called ions. 
These ions are respectively electro-positive or electro-negative, 
and are called kathions and anions. (See Ions. Electrolysis.) 

Radiometer, Crookes' An apparatus for 

showing the action of radiant matter in producing motion 
from the effect of the reaction of a stream of molecules escap- 
ing from a number of easily moved heated surfaces. (See 
Matter, Radiant.) 

Rail Road, or Railway, Electric A rail- 
road, or railway, the cars on which are driven or propelled 
by means of electric motors connected with the cars. 

The electric current that drives the electric motor is either 
derived from storage batteries placed on the cars, or from 
a dynamo-electric machine or battery of dynamo-electric 
machines, conveniently situated at some point on the road. 
(See Storage of Electricity.) The current from the dynamo is led 
along the line by suitable electric conductors. This current is 
passed into the electric motor as the car runs along the 
tracks, in various ways, viz. : 

(1) Placing one or both rails in the circuit of the dynamo and 
taking the current from the tracks by means of sliding or 
rolling contacts connected with the motor. 

(2) By placing the conducting wires parallel to each other 
in a longitudinally slotted undergroumd conduit in the road 
bed, and taking the current by means of a traveling brush or 
roller, called a plow, sled or shoe, and provided with two cen- 
tral plates, insulated from one another and connected re- 
spectively to the motor terminals. On the movement of the 



512 A DICTIONARY OF ELECTRICAL 

car over the track, these traveling contacts touch the two 
parallel line conductors in the conduit, and take the electric 
current therefrom. (See Plow, Sled.) 

(3) By placing the line conductors on poles, along the road, 
and taking the current therefrom by means of suitable travel- 
ing contacts called trolleys or by sliders. (See Trolleys.) 

The first method, viz., that of using the tracks alone as con- 
ductors is not much employed. 

The use of the track and ground as a return for the current 
is now very generally employed. 

In some systems the track is divided into sections which are 
successively brought into action with the main conductors by 
contacts effected by the attraction between magnets carried 
on the car and contact pieces of magnetic material placed be- 
low the surface. The rail section thus temporarily energized 
is placed in connection with the motor. 

In order to regulate the speed, various devices are employed 
to vary the current strength in the motor circuit. These 
devices consist essentially in rheostats or resistances intro- 
duced into, or removed from, the motor circuit by the move- 
ment by hand of a lever that forms part of the circuit, over 
contact plates connected to the resistance coils. 

In order to change the direction of the car, the direction of 
rotation of the electric motor is changed. This is effected by 
some form of reversing gear or mechanism that changes the 
direction of rotation of the motor, either by shifting the 
brushes, by changing the field, or by any other means. (See 
Telpherage. Electric Motor. Rheostat.) 

Ray, Electric (See Fishes, Electric.) 

Rays, Actinic (See Antinic Rays.) 

Reaction Principle of Dynamo-Electric Ma- 
chines o — The reaction of the field magnets and the armature 
of a dynamo-electric machine on each other until the full work- 
ing current which the machine is capable of developing is pro- 
duced. 



WORDS, TERMS AND PHRASES. 513 

When the armature of a series or shunt dynamo commences 
to rotate, the differences of potential generated in its coils are 
very small, since the field of the magnet is so weak. The cur- 
rent so produced in the armature, however, circulating through 
the field magnet coils, increases the intensity of the mag- 
netic field of the machine, and this reacting on the arma- 
ture results in a more powerful current through it. This cur- 
rent again increases the strength of the magnetic field of the 
machine, which again reacts to increase the current strength 
of the armature coils, and this continues until the machine 
is producing the full current it is designed to produce. 

A dynamo-electric machine very rapidly "builds up," or 
reaches its maximum current after starting. The reaction 
principle was discovered by Soren Hjorth, of Copenhagen. 

Reaction Telephone. — An electro-magnetic telephone 
in which the currents induced in a coil of wire attached to 
the diaphragm are passed through the coils of the electro- 
magnet and thus react on and strengthen it. 

Reaetion Wheel, Electric (See Flyer, 

Electric.) 

Reactions, Anodic and Kathodic (See Kath- 

odic and Anodic Reactions.) 

Reading Telescope. — (See Telescope, Reading.) 

Receiver, Harmonic A receiver, employed 

in systems of harmonic telegraphy, containing an electro- 
magnetic reed, tuned to vibrate to one note or tone only. (See 
Telegraphy, Harmonic.) 

Receiver, Phonographic, Telephonic, Grapho- 

phonic, Grainophonic The apparatus employed 

in' a telephone, phonograph, graphophone, or gramophone, 
for the reproduction of articulate speech. (See Phonograph.) 

Reciprocals. — The quotient arising from dividing unity 
by any number. 

The reciprocal of 4 is }-± or .250. 



514 



A DICTIONARY OF ELECTRICAL 



The conducting power of any circuit is equal to the re- 
ciprocal of its resistance, or, in other words, the conducting 
power is inversely proportional to the resistance. 

The following table contains the reciprocals of the numerals 
up to 100 : 

Table of Reciprocals. 



No. 


Recip- 
rocal. 


No. 


Recip- 
rocal. 


No. 


Recip- 
rocal. 


No. 


Recip- 
rocal. 


No. 


Recip- 
rocal. 


2 


0.5000 


22 


0.0455 


42 


0.0338 


62 


0.0161 


82 


0.0122 


3 


0.3333 


23 


0.0435 


43 


0.0233 


63 


0.0159 


83 


0.0120 


4 


0.2500 


24 


0.0417 


44 


0.0227 


64 


0.0156 


84 


0.0119 


5 


0.2000 


25 


0.0400 


45 


0.0222 


65 


0.0154 


85 


0.0118 


6 


0.1667 


26 


0.0385 


46 


0.0217 


66 


0.0152 


86 


0.0116 


7 


0.1429 


27 


0.0370 


47 


0.0213 


67 


0.0149 


87 


0.0115 


8 


0.1250 


28 


0.0357 


48 


0.0208 


68 


0.0147 


88 


0.0114 


9 


0.1111 


29 


0.0345 


49 


0.0204 


69 


0.0145 


89 


0.0112 


10 


0.1000 


30 


0.0333 


50 


0.0200 


70 


0.0143 


90 


0.0111 


11 


0.0909 


31 


0.0323 


51 


0.0196 


71 


0.0141 


91 


0.0110 


12 


0.0833 


32 


0.0313 


52 


0.0192 


72 


0.0139 


92 


0.0109 


13 


0.0769 


33 


0.0303 


53 


0.0189 


73 


0.0137 


93 


0.0108 


14 


0.0714 


34 


0.0294 


54 


0.0185 


74 


0.0135 


94 


0.0106 


15 


0.0667 


35 


0.0286 


55 


0.0182 


75 


0.0133 


95 


0.0105 


16 


0.0625 


36 


0.0278 


56 


0.0179 


76 


0.0132 


96 


0.0104 


17 


0.0588 


37 


0.0270 


57 


0.0175 


77 


0.0130 


97 


0.0103 


18 


0.0556 


38 


0.0263 


58 


0.0172 


78 


0.0128 


98 


0.0102 


19 


0.0526 


39 


0.0256 


59 


0.0169 


79 


0.0127 


99 


0.0101 


20 


0.0500 


40 


0.0250 


60 


0.0167 


80 


0.0125 


100 


0.0100 


21 


0.0476 


41 


0.0244 


61 


0.0164 


81 


0.0123 







{Clark & Sabine.) 

Record, Gramophonic, Graph ©phonic, or Phon- 
ographic The irregular indentations, cuttings, or 

tracings made by a point attached to the diaphragm spoken 
against, and employed in connection with the receiving 
diaphragm for the reproduction of articulate speech. 

Record, Telephonic A permanent record pro- 
duced by the diaphragm of a telephone. 



WOKDS, TERMS AND PHRASES- 



515 



Various methods have been proposed for telephone records, 
but none of them have yet been introduced into actual com- 
mercial use. 

Recorder, Bain's Chemical An apparatus 

for recording the dots and dashes of a Morse telegraphic 
dispatch, on a sheet of chemically prepared paper. 

A fillet of paper soaked in some chemical substance, such 
as ferro-cyanide of potassium, is moved at a uniform rate 
between the two terminals of the line, one of which is iron 
tipped, so that on the passage of the current, a blue dot, or 
dash, will be made on the paper according to the length of 
time the current is passing. 

In order to ensure a moist condition of the paper fillet some 
deliquescent salt, like 
ammonium nitrate, is 
generally mixed with the 
ferro-cyanide of potas- 
sium. 

A Bain Recorder is 
shown in Fig. 326. A, is 
a drum of brass, tinned 
on the outside. The 
paper fillet is drawn 
from the roll and kept pressed against the cylinder A, by a 
small wooden roller B. The needle, which is a metallic point, 
is in connection with one end of the line wire, and the brass 
drum is connected with the other end through the earth. 
Care must be observed to connect the needle point with the 
positive electrode, as otherwise the paper will not be marked. 
The Bain Recorder is now almost entirely replaced by the 
Morse Sounder. 




Recorder, Morse 



or Morse Register.— An 



apparatus for automatically recording the dots and dashes of 
a Morse telegraphic dispatch, on a fillet of paper drawn 



516 



A DICTIONARY OF ELECTRICAL 



under an indenting or marking point on a striking lever, con- 
nected with the armature of an electro-magnet. 

The Morse registering or recording apparatus is shown in 
Fig. 327. 

The paper fillet passes between a pair of rollers r. driven 
by the clockwork W. The upper roller is provided with a 
groove, so that the depression of the stylus at the bent end 
of the lever L, by the electro-magnet M, moving its arma- 
ture attached to the lever L, may indent or emboss the paper 
fillet. When no current is passing, the armature of the 
magnet and the lever L, are drawn back by the action of an 
adjustable spring at n. 

9 




Eig. 327. 

In the drawing, the ordinary Moi'se sounder is shown on the 
right. The sounder has almost entirely replaced the record- 
ing apparatus. 

Recorder, Siphon An apparatus for re- 
cording in ink on a sheet of paper, by means of a fine glass 
siphon supported on a fine wire, the message received over a 
cable. 

One end of the siphon dips in a vessel of ink. The record is 
received on a fillet of paper moved mechanically under the 
siphon. The ink is discharged from the siphon by electric 
charges imparted to the ink by a static electric machine. 



WORDS, TERMS AND PHRASES. 



517 



In the annexed sketch of the siphon recorder, Fig. 328, a light 
rectangular coil b b, of very fine wire, is suspended by a 
fine wire//', between the poles N, S, of a powerful com- 
pound permanent magnet, and moving on the vertical axis 
of the supporting wire//', adjustable as to tension, at h. 
A stationary soft iron core a, is magnetized by induction 




Fig. 



and strengthens the magnetic field of N, S. The cable cur- 
rent is received by the coil b b, through the suspending wire 
//', and is moved by it to the right or the left, according 
to its direction, to an extent that depends on the current 
strength. 

The fine glass siphon n, which dips into a reservoir of ink at 
m, is capable of movement on a vertical axis I, and is moved 
backwards or forwards, in one direction by a thread k, 



518 



A DICTIONARY OF ELECTttlCAF 



attached to b, and in the opposite direction by a retractile 
spring- attached to an arm of the axis /. 

As the paper is moved under the point of the siphon, an 
irregular curved line is marked thereon. 

Two records as actually received by a siphon recorder are 
shown in the Figs. 329 and 330. Movements upwards corre- 
spond to the dots, and downwards to dashes. 

Rectilinear Currents. (See Currents, Rectilinear.) 

Reflecting Galvanometer.— (See Galvanometer, Re- 
flecting.) 

Reflector, Parabolic 

Hector.) 



— (See Parabolic Re- 




S I PHON RECORDER 
Fig. 329. 

Refraction, Double 



Reflectors. — 

Plane or curved sur- 
faces capable of regu- 
larly reflecting light. 
(See Parabolic Re- 
flectors.) 
The property possessed 

by certain bodies of splitting up by refraction a ray of light 

passed into it, into two separate 

rays, and thus doubly refract- " "¥Dl 

. ' J SETTLE D 

ing it. 

Certain specimens of calc spar ig - ' m 

possess the property of double refraction. Each of the two 

rays into which the original ray is separated is polarized. 

Refraction, Double Electric The prop- 
erty of doubly refracting light acquired by some transparent 
substances when placed in an electrostatic or electro-magnetic 
field. (See Double Refraction, Electric.) 

Register, Watchman's Electric —(See Watch- 
man's Register, Electric.) 



Registering Apparatus, Electric 



-De- 



vices for obtaining permanent records by electrical means. 
(See Recorders.) 



WORDS, TERMS AND PHRASES. 



519 



Regulation, Automatic — (See Automatic 

Regulation.) 

Relative Calibration.— (See Calibration, Absolute and 
Relative.) 

Relay Bell.— (See Bell, Relay.) 

Relay, Microphone (See Microphone Relay.) 

Relay, or Receiving Magnet. — An electro-magnet 
employed in systems of telegraphy provided with contact- 
points, placed on a delicately supported armature, the move- 
ments of which throw a battery, called the local battery, into 
or out of circuit, for the operation of the recording apparatus. 




Fig. 331. 
The use of a relay permits much smaller currents to be 
used than could otherwise be done, since the electric impulses, 
on reaching a distant station, are required to do no other work 
than attracting a delicately poised movable contact, and thus, 
by throwing a local battery into the circuit of the receiving- 
apparatus, to cause such local battery to perform the work of 



520 A DICTIONARY OF ELECTRICAL 

registering. Its use is especially required in the Morse system 
of telegraphy in order to cause the Sounder to be distinctly 
heard. 

A form of relay much used is shown in Fig. 331. 

The electro-magnet M, is wound with many turns of very 
fine wire. In the form used by the Western Union Telegraph 
Company, there are about 8,500 turns, having resistance of 
150 ohms. A screw m, is provided for moving the electro- 
magnet M, a slight distance in or out for the purposes of ad- 
justment. A semi-cylindrical armature A, of soft iron, is 
attached to the insulated armature lever a, the lower end of 
which is supported by a steel arbor, which is pivoted between 
two set screws. A retractile spring S', regulable at S, is pro- 
vided for moving the armature away from the electro-magnet. 
There are four binding posts, two of which are placed in the 
circuit of the electro-magnet, and two in that of the local 
battery. The ends of the line wire are connected with the 
former, and the receiving instrument placed in the circuit of 
the latter. A platinum contact is placed on the end of a screw 
supported at F, opposite a similar contact, near the end a, of 
the armature lever. The contact is regulable by means of 
a screw c. 

On the the energizing of the electro-magnet, the attraction 
of its armature closes the platinum contact, and by thus com- 
pleting the circuit of the local battery causes an attraction of 
the armature of the receiving apparatus. On the cessation of 
the current in the main line, the spring S', pulls the armature 
away from the magnet, breaks the current of the local battery, 
and thus permits a similar spring on the receiving instrument 
to pull its armature away. Thus all the movements of the 
armature of the relay are reproduced with increased intensity 
by the armature of the receiving instrument. 

The connections of the relay to the local battery and the 
registering apparatus, will be better understood from an in- 
spection of Fig. 332, which represents a form of relay much 



WORDS, TERMS AND PHRASES. 



521 



used in Germany. The retractile spring /, is regulated by 
the up-and-down movements of its lower support, which slides 
in the vertical pillar S. The line wire is shown at m ra, con- 
nected at one end to earth by the ground wire. The register- 
ing apparatus, R, is connected in the circuit of the local bat- 
tery L, as shown. The contacts are made by the end B, 
of the lever B B', attached to the armature A, of the electro- 
magnet M M. 




Fig. 332. 



-A telegraphic relay provided 



Relay, Polarized 

with a permanently magnetized armature in place of the soft 
iron armature of the ordinary instrument. 

In the form of polarized relay shown in Fig. 333, N S, is a 
steel magnet, whose magnetism is consequently permanent, 
with its north and south poles at N and S, respectively. The 
cores of the electro-magnet m m', are of soft iron, and, since 
they rest on the north pole N of the permanent steel magnet 



o22 



A DICTIONARY OF ELECTRICAL 



the poles, brought very near together by the armatures at 
n, n', will be of the same polarity as N, when no current is 
passing through the coils m, m' ; but when such current does 
pass, one of these poles becomes of stronger north polarity, 
while the other changes its polarity to south. By this means 
to-and-fro movements of the armature lever with its contact 
point are effected without the use of a retractile spring ; 
movement in one direction occurring on the closing of the 
circuit through the electro-magnetism developed by the coils 




Fig. 333. 

m, w! , and movement in the opposite direction, on the losing 
of this magnetism on breaking the circuit, by the permanent 
magnetism of the steel magnet N S. These movements are 
imparted to the soft iron lever c c', pivoted at B, and passing 
between the closely approached soft iron poles at n, n'. This 
lever rests at the end c' against a contact point when moved 
in one direction, and against an insulated point when moved 
in the opposite direction. It rests against the insulated point 
when no current is passing through the coils m, m'. 
If the armature lever were placed in a position exactly mid- 



WORDS, TERMS AND PHRASES. 523 

way between the poles n and n', it would not move at all, 
being- equally attracted by each ; but if moved a little nearer 
one pole than the other, it would be attracted to, and rest 
against, the nearer pole. 

When alternating currents are employed on the line, the 
lever c c' must be adjusted as nearly as possible in the middle 
of the space between nand n', in which case it will remain on 
the side to which it was last attracted, until a current in the 
opposite direction moves it to the other side. 




LB 

Fig. 33U. 

The space between „ne magnet poles n, n' , and the contacts 
of the armature lever at D and D', are shown in detail in 
Fig. 334, which is a plan of the preceding figure. The bind- 
ing posts, for the line battery are shown at LB, and those 
for the local battery at O, B. The dotted lines show the con- 
nections. 

Since the polarized relay dispenses with the retractile 
spring, it is far more sensitive than the ordinary instrument. 



524 



A DICTIONARY OP ELECTRICAL 



Once adjusted no further regulation is required, in which re- 
spect, it differs very decidedly from non-polarized relays. 

Reluctance, Magnetic (See Magnetic Re- 
luctance.) 



Repeaters, Telegraphic 



— Teregraphic de- 



vices, whereby the relay, sounder, or registering apparatus 
is caused to repeat the signals received, by opening and clos- 
ing another circuit with which it is suitably connected. 




Fig. 385. 

Repeaters are employed to establish direct communication 
between very distant stations, or to connect branch lines to 
the main line. 

Fig. 335, shows Wood's Button Repeater. This repeater 
consists simply of a three-point-switch L, capable of being 



WORDS, TERMS AND PHRASES. 



525 



placed on the points 1, 2 and 3 ; and a ground switch at 4. 
The circuits are arranged between the sounders S, S', relays 
M, M', main batteries 
B, B', and the two main 
lines E and W, in the 
manner shown. 

If the lever L, is in 
the position shown in 
the drawing, the lines 
E and W, form inde- 
pendent circuits. 

If the ground switch 
4 is closed, and the 
lever L is placed on 2, 
2, the eastern line re- 
peats into the western. 
If the lever L is placed 
on the plates 3, 3, the 
western line repeats 
into the eastern. 

This repeater is non- 
automatic and can be 
worked in but one di- 
rection ; morever, it re- 
quires the services of an 
attendant. 

The automatic repeat- 
er can be operated in 
both directions, and dis- 
penses with the con- 
stant services of an at- 
tendant at the repeat- 
ing station. 

In sending a dispatch 
through a repeater, the dots and dashes are prolonged so as to 




526 



A DICTIONARY OF ELECTRICAL 



give the lever of the repeating instrument time in which 
to move backwards and forwards. 

In Hi'cks 1 Automatic Button Repeater, shown in Fig. 336, 
the switch or circuit changer is automatic in its action. 

The relay magnets are shown at M, M', the sounders at R, 
and R' ; /, /', are platinum contacts operated by levers I and V, 
and L and L' are Extra Local Magnets, that act on armatures 
placed directly opposite the armatures of the relay magnets. 

The extra local magnet L is cut 
out of the circuit of B', the Extra 
Local Battery, when the main cir- 
cuit is broken, and the armature is 
in contact with c. As soon as this 
happens, however, the spring s, 
drawing away the armature, and 
thus opening the short circuit of 
no resistance between c and a, 
establishes a circuit through L. 
On a coming in contact with c, 
the circuit is again broken. The 
tension of the spring s is so regu- 
lated that a very rapid vibration 
of a is so constantly maintained, 
that it is impossible to close the 
main circuit when L is not cut 
out. The armature a will there- 
fore respond to very weak impulses 
of the relay magnet. 

On breaking the western main 
circuit N, the lever a vibrates 
I, of the sounder R, first breaks 
the circuit of L, and afterwards that of the eastern main 
circuit E, which passes though M. Both L' and M', be- 
ing broken, a slight tension of s', will hold a, in place, thus 
avoiding the breaking of the western main circuit through 




Fig. 837. 
very rapidly. The lever 



WOUDS, TERMS AND PHRASES. 527 

the closing- of the local circuit through R. On the closing- of 
the western circuit, the reverse of these operations occur. 

The author has taken the above explanation mainly from 
Pope's work on " Modern Practice of the Electric Tele- 
graph." 

Replenisher, Thomson's A static influ- 
ence machine devised by Sir Wm. Thomson for charging- the 
quadrants of his quadrant electrometer. 

Two brass carriers C and D, shown in Fig. 337, are ec- 
centrically fixed to the end of the vulcanite rod E, which is 
capable of rotation by the thumb screw at M, in the direction 
shown by the arrow. Hollow metal half cylinders, A and B, 
act as inductors, a strip of brass fixed around the edges of a 
piece of vulcanite P, connecting the metallic springs S and S', as 
shown. The action of the replenisher is readily understood 
from the following considerations, as suggested by Ayrton in 
his " Practical Electricity" : 

A and B, Fig. 338, are two insulated hollow metallic vessels 
having a small difference of potential between them, A, being 
the higher. C and D, are two small uncharged conductors 
held by insulating strings. If C and D be held near A and 
B, as shown, the potential of C will, by induction, be raised 
somewhat above that of D, so that when connected by a con- 
ductor, such as the metallic wire W, a small quantity of 
positive electricity will flow from C to D, thus leaving D 
positively, and C negatively charged. 

If, now, C and D, are removed from W and placed in the 
bottom of B and A, as shown in Fig. 339, the difference of 
potential between A and B, will be thereby increased, and if 
they are then withdrawn, and totally discharged, and again 
placed in the first position shown, an additional charge 
can be given to A and B, and this can be repeated as often as 
desired. 

In the replenisher, A and B correspond to the vessels A 
and B; the brass carriers C and D, to the balls C and D, 



528 



A DICTIONARY OF ELECTRICAL 



and the spring S S, and M, to the wire W. No initial charge 
need be given to A and B, since they are invariably found 
to be at a sufficient difference of potential to build up the 
charge. 

Residual Atmosphere.— (See Atmosphere, Residual.) 
Residual Charge.— (See Charge, Residual.) 
Residual Magnetism. — The magnetism remaining in 
the core of an electro-magnet on the opening of the magnetiz- 
ing circuit. 

Resin. — A general term applied to a variety of dried 
juices of vegetable origin. 

Resins are, in general, transparent, inflammable solids, 
soluble in alcohol, and are non-conductors of electricity. Rosin 
is one of the varieties of resin. 





Fig. 338. 

Resinous Electricity. — A term formerly employed in 
place of negative electricity. 

It was at one time believed that all resinous substances are 
negatively electrified by friction. This we now know to be 
untrue, the nature of electrification depending as much on 
the character of the rubber, as on the character of the thing 



WORDS, TERMS AND PHRASES. 



529 



rubbed. Thus resins rubbed with cotton, flannel or silk, be- 
come negatively excited, but rubbed with sulphur or gun- 
cotton, positively excited. The terms positive and negative 
are now exclusively employed. 

Resistance Box. — A box containing a number of coils of 
known resistances employed for determining the value of an 
unknown resistance. (SeeBo.v, Resistance. Balance, Electric, 
Box Form of.) 

Resistance Coil. — A coil of insulated wire of known 



the external effects of its own magnetic field. 
sistance.) 

Resistance Coil, Standard 



(See Coils, Re- 



coil 



the resistance of which is that of the standard ohm. 

The standard ohm, as issued 
by the Electric Standards Com- 
mittee of England, has the 
form shown in Fig. 340. The 
coil of wire is formed of an 
alloy of platinum and silver, 
insulated by silk covering and 
melted paraffine. Its ends are 
soldered to thick copper rods 
r, ?•', for ready connection with 
mercury cups. The coil is at 
B. The space above it at A is 
filled with paraffin, except at 
the opening t, which is provided for the insertion of a ther- 
mometer 

Resistance, Effect of Heat on Electric 

Nearly all metallic conductors have their electric resistance 
increased by an increase of temperature. 

The carbon conductor of an electric incandescent lamp on the 
contrary, has its resistance decreased when raised to electric 




Fig. SAO. 



530 



A DICTIONARY OF ELECTRICA, 



incandescence. The decrease amounts to about three-eighths 
of its resistance when cold. 

The effects of heat on electric resistance may be sum- 
marized as follows : 

(1) The electric resistance of metallic conductors increases 
as the temperature rises. (Carbon is an exception). 

(2) The electric resistance of electrolytes decreases as the 
temperature rises. 

(3) The electric resistance of dielectrics and non-conductors 
decreases as the temperature rises. 

Resistance and Conductivity of Pure Copper at Different 
Temperatures. 



Centigrade 






Centigrade 






Tempera- 


Resistance. 


Conductivity. 


Tempera- 


Resistance. 


Conductivity. 


ture. 






ture. 






0° 


1.00000 


1.00000 


16° 


1.06168 


.94190 


1 


1.00381 


.99624 


17 


1.06563 


.93841 


2 


1.00756 


.99250 


18 


1.06959 


.93494 


3 


1.01135 


.98878 


19 


1.07356 


.93148 


4 


1.01515 


.98508 


20 


1.07742 


.92814 


5 


1.01896 


.98139 


21 


1.08164 


.62452 


6 


1.02280 


.97771 


22 


1.08553 


.92121 


7 


1.02663 


.97406 


23 


1.08954 


.91782 


8 


1.03048 


.97042 


24 


1.09365 


.91445 


9 


1.03435 


.96679 


25 


1.09763 


.91110 


10 


1.03822 


.96319 


26 


1.10161 


.90776 


11 


1.04199 


.95970 


27 


1.10567 


.90443 


12 


1.04599 


.95603 


28 


1.11972 


.90113 


13 


1.04990 


.95247 


29 


1.11382 


.89784 


14 


1.05406 


.94893 


30 


1.11782 


.89457 


15 


1.05774 


.94541 









(Latimer Clark.) 

The following table from Matthiessen's measurements giv( 
the relative resistances of equal lengths and cross sectioi 



WORDS, TERMS AND PHRASES. 



531 



of different substances as compared with silver. The sub- 
stances are chemically pure. 

Legal Microhms. 





Resistance in Microhms atO° C. 


Relative 
Resistance. 


Names op Metal. 


CenUmetre. J Cubic inch. 


Silver, annealed 

Copper, annealed 

Silver, hard drawn 

Copper, hard drawn... 

Gold, annealed 

Gold, hard drawn 

Aluminium, annealed. 
Zinc, pressed . 


1.504 
1.598 
1.634 
1.634 
2.058 
2.094 
2.912 
5.626 
9.057 
9.716 
12.47 
13.21 
19.63 
20.93 
35.50 
94.32 
131.2 


0.5921 
0.6292 
0.6433 
0.6433 

0.8102 

0.8247 

1.1470 

2.215 

3.565 

3.825 

4.907 

5.202 

7.728 

8.240 

13.98 

37.15 

51.65 


1. 

1.063 
1.086 
1.080 
1.369 
1.393 
1.935 
3.741 


Platinum, annealed... 

Iron, annealed 

Nickel, annealed 

Tin, pressed.. 

Lead , p ressed 

German Silver 

Antimony, pressed 

Mercury 


6.022 
6.460 
8.285 
8.784 
13.05 
13.92 
23.60 
62.73 


Bismuth, pressed 


87.23 



(Ayrton.) 

The above resistances are for chemically pure substances 
only. Slight impurities produce very considerable changes 
in the resistance. 



Re§istance, Electric The ratio between 

the electro-motive force of a circuit and the current that 
passes therein. 

Ordinarily the resistance of a circuit may be conveniently 
regarded as that which opposes or resists the passage of the 



532 A DICTIONARY OF ELECTRICAL 

current. Strictly speaking, however, this is not true, since 
from Ohm's law (See Ohm's Law), 
E 
C = — , from which we obtain 
R 
E 
R = — , which shows that resistance is a ratio between 
C 
the electro-motive force that causes the current and the 
current so produced. 

Resistance may be expressed as a velocity. The dimensions 
of resistance in terms of the electro-magnetic units are 

L 

T ' 
(See Units, Electro-Magnetic.) But these are the dimensions of 
a velocity which is the ratio of the distance passed over in unit 
time. Resistance may therefore be expressed as a velocity. 

" The resistance known as ' one ohm ' is intended to be 10 9 
absolute electro-magnetic units, and therefore is represented 
by a velocity of 10 9 centimetres or ten million metres (one 
earth-quadrant) per second " — Sylvanus Thompson. 

Resistance may be represented by a velocity, one ohm being 
the resistance of a wire, which, if moved through a unit field 
of force at the rate of ten million (10 9 ) centimetres per second 
will have a current of one ampere generated in it. (See Ohmic 
Resistance. Spurious Resistance. 

The unit of resistance is the ohm. Its true value, as has 
been shown by careful measurements, is not exactly equal to 
10 9 centimetres per second. 

Resistance, Electric of Liquids.— The resist- 
ance offered by a liquid mass to the passage of an electric 
current. 

As a rule the electric resistance of a liquid is enormously 
higher than that of metallic bodies, with the single exception 
of mercury. 

To determine the resistance ®f a liquid, a section is taken 



WORDS, TERMS AND PHRASES. 



533 



between two parallel metallic plates A and B, Fig. 341, 
placed as shown in the figure, and an electric current is 
passed between them. In order to avoid the effect of a spur- 
ious resistance, due to a counter electro-motive force, it is 
necessary to use plates at A and B, of metals that are not 
acted on chemically by the liquid on the passage of the current. 
(See Counter Electro-Motive Force. Spurious Resistance.) 
In order to more accurately vary the size of the plates 
immersed in the liquid, and hence the area of cross section of 
the liquid conductor, as well as the distance between the 
plates, the apparatus shown in Fig. 342 may be used, in which 
these distances are readily adjustable, as shown. 

Resistance, Magnetic (See Magnetic Resistance.) 

Resistance, Measurement of Methods em- 
ployed for determining the resistance of 
any circuit or part of a circuit. 

Numerous methods are employed for 
this purpose. Among these are : 

(1) The use of a Resistance Box with a 
Wheatstone's Bridge, by opposing or bal- 
ancing the unknown resistance against a 
known resistance. (See Balance, Wheat- 
stone's.) 

(2) With the Differential Galvanometer. 
(See Galvanometer, Differential.) 

(3) By the Method of Substitution. 

(4) By a Comparison of the Deflections 
of a Galvanometer. 

Method of Substitution — A resistance 
box R, Fig. 343, galvanometer G, and the 
resistance x, that is to be measured, 
Fig. Ski. are placed in the direct circuit of the 

battery B by means of conductors of such thick wire that 
their resistance can be neglected. The deflection of the gal- 
vanometer is first measured with x in circuit, and no resist- 




534 



A DICTIONARY OF ELECTRICAL 



ance in the box R. The resistances is then cut out of the 
circuit by placing a thick copper wire across the terminals of 
the mercury cups at m, m', and resistances unplugged in R, 
until the same deflection is obtained. Then, if the electro- 




Fig. 3U2. 
motive force of the battery has remained constant, the resist- 
ances unplugged equal the unknown resistance. 

For full description of the various methods of determining 
resistance the reader is referred to " Ayr-ton' 8 Practical Elec- 
tricity," "Kempe's Handbook of Testing," or other standard 
electrical books. 
x 

9 I I o o o o "\ 



m' 



M'lt 



Resistance, Olim- 

i c (See 

Ohmic Resistance.) 
Resistance, Spur- 

(See 



Fig. 3h3. 
equal lengths and cross sections of 
given in ohms, or other units of resistance : 



ious 

Spurious Resistance.) 

Resistance, Tab- 
les of Tables in 

which the resistance of 
different substances is 



WORDS, TERMS AND PHRASES. 



535 



Resistance. 
Resistance of Wires of Pure Annealed Copper at O r 
{Density = 8.9.) 



a . 




_, U fl>^~. 


Resistance of Wire of Pnre Annealed 


*i i 




.£&££ 




Copper at 0° C. 


3 ^ 


fee « 2 


5=0 |fe 

e£3 M® 








l| 


Ohms 


Metres 


Ohms 


£^1 


J *3B 


per 


per 


per 


5S 


£ O 


Kilometre. 


Ohm. 


Kilogramme. 


5 


175 


5.7 


.8 


1230.5 


.00456 


4.4 


135.28 


7.4 


1.06 


944.38 


.00784 


3.9 


106.35 


9.5 


1.35 


722 


.0128 


3.4 


80.8 


12.5 


1.80 


563.92 


.0222 


3 


62.93 


16 


2.3 


439.07 


.0365 


2.7 


51 


19.8 


2.8 


355.65 


.0557 


2.4 


40.23 


25 


3.6 


281 


.088 


2.2 


33.82 


29 


4.2 


236.08 


.123 


2 


27.95 


36 


5.1 


195.15 


.185 


1.8 


22.7 


44 


6.3 


158.08 


.278 


1.6 


17.89 


56 


8 


124.9 


.448 


1.5 


15.75 


63 


9.1 


109.75 


.574 


1.4 


13.7 


73 


10.5 


95.651 


.763 


1.3 


11.84 


85 


12 


82.42 


1.03 


1.2 


10.06 


100 


14 


70.247 


1.42 


1.1 


8.47 


119 


17 


59.024 


2.02 


1 


6.99 


144 


20 


48 782 


2.95 


.9 


5.66 


178 


25 


39.515 


4.19 


.8 


4.47 


225 


32 


31.225 


7.21 


.7 


2.83 


294 


42 


23.9 


12.3 


.6 


2.52 


400 


57 


17.56 


22.78 


.5 


1.74 


576 


81 


12.305 


46.81 


.4 


1.175 


902 


122.4 


8.173 


110.41 


.34 


.808 


1251 


177.9 


5.622 


222.55 


.3 


.7181 


1607 


228.5 


4.377 


367.2 


.24 


.4026 


2508 


357 


2.801 


895.36 


.2 


.2797 


3614 


514 


1.945 


1,857.6 


.16 


.179 


5590 


803.1 


1.245 


4,489 


.12 


.1007 


9929 


1428 


.7 


14,179 


.1 


.0699 


14369 


2056 


.486 


29,549 


.08 


.0447 


24570 


3213 


.311 


78,943 


.06 


.0252 


39824 


5713 


.173 


227,515 


.04 


.0112 


88878 


12848 


.078 


1,142,405 



(Hospitalier.) 



536 



A DICTIONARY OF ELECTRICAL 



Table of Conducting Powers and Resistances in Ohms. 







a> v 


<v a> 






*S bo" 




O 


c 5 
o o 


a a 
o o 


p— 1 


a £ 
o a> 


-1 




o 


a> be 


CD b£ 


£S 


8 J 


SPSS 




t-, 


£2 
bt 


&-P 


* o 


*| 


a si t- 




£ 


os 3 


83 4> 


S3 o 


o3 a) 


S322 


Names of Metals. 


O 


._ £ 


£ 


"N. 


<*- o . 


ft"g, 




a 

1 

■a 


o 
be 

a> p 

%S . 

-2^ 2 
.2 o'S 


O bfl 

a 

Is! 


o 

IIS 

2 - § 


bc<u 
° ° p 


<tf "" » 




a 
o 


££& 


I s " 


3 3-2 


£S.S 


ag-? 




O 


IS 


W 


w 


^>- 


Silver, annealed 




0.2214 


0.1544 


9.936 


0.01937 


0.377 


Silver, hard drawn... 


100.00 


0.2421 


0.1689 


9.151 


0.02103 




Copper, annealed 




0.2064 


0.1440 


9.718 


0.02057 


0.388 


Copper, hard drawn. . 
Gold, annealed 


99.55 


0.2106 


0.1469 


9.940 


0.02104 






0.5849 


0.4080 


12.52 


0.02650 


0.355 


Gold, hard drawn 


77.96 


0.5950 


0.4150 


12.74 


0.02697 




Aluminium, annealed 




0.06822 


0.05759 


17.72 


0.03751 




Zinc, pressed 


29.02 


0.5710 


0.3983 


32.22 


0.07244 


0.365 


Platinum, annealed. . 




3.536 


2.464 


55.09 


0.1166 




Iron, annealed 


16.81 


1.2425 


0.7522 


59.40 


0.1251 




Nickel, annealed. .. 


13.11 


1.0785 


0.8666 


75.78 


0.1604 




Tin, pressed 


12.36 


1.317 


0.9184 


80.36 


0.1701 


0.365 


Lead, pressed 


8.32 


3.236 


2.257 


119.39 


0.2527 


0.387 


Antimony, pressed. . . 


4.62 


3.324 


2.3295 


216.0 


0.4571 


0.389 


Bismuth, pressed.. . 
Mercury, liquid . . 


1.24 


5.054 


3.525 


798.0 


1.689 


0.354 




18.740 


13.071 


600.0 


1.270 


0.072 


Platinum-silver, a 1 - 














loy, hard or annealed 




4.243 


2.959 


143.35 


0.3140 


0.031 


German silver, hard 














or annealed 




2.652 


1.850 


127.32 


0.2695 


0.044 


Gold, silver, alloy, 






hard or annealed. . . 




2.391 


1.668 


66.10 


0.1399 


0.065 









(Jenkin.) 



When several resistances are placed in series in any circuit, 
by measuring the difference of potential at their terminals, 
their values can be determined by simple calculation, being 
directly proportional to these differences of potential. This 
method in especially applicable to the measurement of such 
low resistances as the armatures of dynamo electric machines. 

Resultant. — In mechanics, a single force that represents 



WORDS, TERMS AND PHRA.SES. 537 

in direction and intensity the effects of two or more forces 
acting in different directions. 

Retardation. — A decrease in the speed of telegraphic 
signaling caused by the induction of the line conductor on 
itself, and the induction between it and neighboring con- 
ductors. 

Retardation in signaling is produced by the following 
causes : 

(1) Self-induction which produces extra currents. (See 
Self-induction. Currents, Extra.) 

The extra current on making, retards the beginning of the 
signal, and the extra current on breaking, retards its stopping. 

(2) Mutual Induction between the line conductor and neigh- 
boring conductors. The line must receive a certain charge 
before a current sent into it at one end can produce a signal at 
the other end. This charge will depend on the length and 
surface of the wire, on its neighborhood to the earth or other 
wires, and on the nature of the insulating material between it 
and the neighboring' conductor. This results in a charg'e given 
to the wire which is lost as a current for signaling. The 
greater the electrostatic capacity of the line wire, the greater 
will be the retardation in signaling. (See Capacity, Specific 
Inductive. Dielectric. Electrostatic Capacity.) 

(3) The Magnetic Inertia or Lag, or the time required to 
magnetize or demagnetize the core of the electro-magnetic 
receptive devices used on the line. 

Retentivity, Magnetic A term proposed by 

Lamont in place of coercive force, or the power possessed by 
a magnetizable substance of resisting magnetization or 
demagnetization. (See Coercive Force.) 

Return Shock or Stroke. (See Back Stroke.) 

Reverse Induced Current. — The current produced by 
self-induction in a circuit at the moment of completing the 
circuit. (See Extra Current.) 



538 A DICTIONARY OF ELECTRICAL 

Reversing Gear of Electric Motor.— Apparatus for 
reversing the direction of the current through an electric 
motor, and, consequently, the direction of its rotation. (See 
Railroad or Railway, Electric.) 

Reversing Key.— (See Key, Reversing.) 

Rheochord.— (See Rheostat.) 

Rlieometer.— A term formerly employed for any device 
for measuring the strength of a current. (Now obsolete and 
replaced by the word Galvanometer.) 

Rheomotor. — A term formerly employed to designate 
any electric source. (Now obsolete and replaced by the various 
names of the different electric sources. (See Source, Electric.) 

Rheophore. — A term formerly employed to indicate a 
portion of a circuit conveying a current and capable of deflect- 
ing a magnetic needle placed near it. (Now obsolete.) 

Rheoscope. — A term formerly employed in place of the 
present word Galvanoscope, for an instrument intended to 
show the presence of a current, or its direction, but not to 
measure its strength. (Now obsolete.) 

Rheostat. — A term signifying any adjustable resistance. 

A rheostat enables the resistance to be brought to a stand, 
i. e., to a fixed value ; hence the name. 

The term rheostat is applied generally to a readily variable 
resistance, the varying values of which are known. 

Rheostat, Wheats tone's A form of appa- 
ratus sometimes employed for an adjustable resistance. 

This apparatus is very seldom employed in accurate work. 

The parallel cylinders A and B, Fig. 344, are respectively of 
conducting and non-conducting materials, the bare wire on 
which can be wound from either cylinder to the other. When 
introduced into a circuit, only the resistance of the portions 
of the wire on B is introduced into the circuit, since the bare 
wire on A is short circuited by the metallic cylinder. This 



WORDS, TERMS AND THRASES. 



539 



rheostat is seldom employed in accurate measurements ow- 
ing to the difficulty of invariably obtaining- reliable contacts. 

Rheostatic Machine. — A machine devised by Plant e in 
which continuous static effects of considerable intensity are 
obtained by charging a number of condensers in multiple arc 
and discharging them in series. 

The condensers are charged by connecting them with a 
number of secondary 
or storage batteries- 

Rlieo tome .—A 
term formerly em- 
ployed for any device 
by means of which a 
circuit could be peri- 
odically interrupted. 
(Now obsolete and re- 
placed by Interrupt- 
er.) 

Rlieotrope. — A 
term formerly em- 
ployed for any device 
by which the current m &- 3kU - 

could be reversed. (Now obsolete and replaced by Commuta- 
tor or Current Reverser.) 

Rhigolene. — A volatile hydro-carbon obtained during the 
distillation of coal oil, and emploj'ed in the flashing, or treat- 
ment of carbons. (See Flashing of Carbons.) 

Rhumbs of Compass. — The thirty-two points of the 
mariners' compass. (See Points of Compass.) 




Rigidity, Molecular 



-Resistance offered by 



the molecules of a substance to rotation, or displacement. 

The molecular rigidity of a magnetizable substance is now 
generally considered to be the cause of differences of coercive 



540 A DICTIONARY OF ELECTRICAL 

force or magnetic retentivity. (See Coercive Force. Reten- 
tivity, Magnetic.) 

Rings, Nobili's (See Metallochromes.) 

Rods, Lightning (See Lightning Rods.) 

Rotation, Electro magnetic (See Accumu- 
lator. Disc, Arago's. Disc, Faraday's. Motors, Electric.) 

Rotation, Magneto-Optic (See Magneto- Optic 

Rotation. 

Rubber of Electrical Machine.— A cushion of 
leather, covered with an electric amalgam, and employed 
to produce electricity by its friction against the plate or cylin- 
der of nfrictional electric machine. (See Machine, Frictional. ) 

Ruhmkorff Coils.— (See Induction Coils.) 

Saddles, Telegraphic Brackets placed on the 

top of telegraph poles, for the support of the insulators. 

Saddle brackets are usually employed for the wire attached 
to the top of a telegraph pole. (See Poles, Telegraphic.) 

Safety Catch, Safety Device, Safety Fuse, Safety 
Plug or Safety Strip for Multiple Circuits.— A wire, 
bar, plate, or strip of readily fusible metal, capable of conduct- 
ing, without fusing, the current ordinarily employed on the 
circuit, but which fuses, and thus breaks the circuit, on the 
passage of an abnormal current. (See Lamp, Incandescent.) 

Safety Device for Arc Lamp, or Series Circuits.— 

Mechanism which automatically provides a path for the 
current around a lamp, or other faulty electro-receptive de- 
vice in a series circuit, and thus prevents the opening of the 
entire circuit on the failure of such device to operate. (See 
Lamp Arc, Electric.) 

Safety Lamp, Electric An incandescent 

electric lr,mp, with thoroughly insulated leads, employed in 



WORDS, TERMS AND PHRASES. 541 

mines, or other similar places, where the explosive effects of 
readily ignitable substances are to be feared. Such lamps are 
often directly attached to a portable battery. 

Salts, Electrolysis of The decomposition of a 

salt into its electro positive and negative radicals or ions. 
(See Electrolysis.) 

Saturation, Magnetic The maximum mag- 
netization which can be imparted to a magnetic substance. 

In an electro-magnet, such a degree of magnetization, that 
any further increase of the magnetizing current, increases the 
magnetic intensity only to the comparatively small extent of 
the increase of the magnetic field due to the current itself. 
(See Magnetic Saturation.) 

Scratch Brush. — A brush furnished with metallic 
bristles, and employed for cleansing the surfaces of metallic 
objects prior to their being electro-plated. 

Screen, Methven's Standard (SeeMethven's 

Standard Screen.) 

Screen or Shield, Electric A closed con- 
ductor, placed over a charged body to screen or protect it from 
the effects of external electrostatic fields, 

The ability of a closed, hollow conductor to act as a screen, 
arises from the fact that all points on its inner surface are at 
the same potential, and therefore are not affected by an in 
crease or decrease in the potential of the outside of the con- 
ductor as compared with that of the earth. (See Net. Fara- 
day's.) 

No considerable thickness is required for the efficient opera- 
tion of an electric screen. 

Screen or Shield, Magnetic (See Magnetic 

Screen or Shield.) 

Screws, Binding or Binding Posts — (See 

Binding Posts.) 



542 A DICTIONARY OF ELECTRICAL 

Seal, Hcrmetical (See Hermetical Seal.) 

Search- Lights, Electric (See Lighthouse 

Illumination.) 

Secondary Batteries.— Arrangements of voltaic cells 
that derive tlieir differences of electric potential from the 
action of an electric current sent through them from a sep- 
arate source, (See Storage of Electricity.) 

Secondary Clocks. — (See Clocks, Secondary.) 

Secondary Currents.— The currents induced in the 
secondary coil of an induction apparatus. (See Induction 
Coils.) 

In the United States this term is also applied to the cur- 
rents derived from secondary batteries. The word is generally 
employed m the former sense. 

Secondary Generators. —A term sometimes employed 
for transformers or converters. (See Transformers or Con- 
verters.) 

Seismograph, Electric An apparatus for 

electrically recording the direction and intensity of earth- 
quake shocks. 

Selenium.— A comparatively rare element generally 
found associated with sulphur. 

Selenium Cell- — A photo-electric couple consisting of 
selenium in combination with another metal usually copper, 
and capable of producing a current by the direct action of 
light. 

Selenium Cell, or Resistance.— A mass o' crystalline 
selenium, the resistance of which is reduced by placing it in 
leform of narrow strips between the edges of broad conduct- 
ing plates of brass. 

The selenium employed for this purpose is the vitreous 
variety, which has been fused and maintained for several 



WORDS, TERMS AND PHRASES. 



543 



hours at about 220° C. by means of which its resistance is 
reduced. 

By exposure to sun-light, the resistance of a selenium cell 
is decreased fully one-naif its resistance in the dark. The 
selenium cell is used in the Photophone. (See Photophone.) 

Selenium Eye. — An artificial eye in which a selenium 
resistance takes the place of the retina and two slides the 
place of the eyelids. 

The selenium resistance is placed in the circuit of a battery 
and a galvanometer. When the slides L,L, Fig. 345, are shut, 
the galvanometer deflection is less than when they are open. 

The opening of 
the aperture be- B 

tween the slides ^ Y ^ / ^ / \\L 

L, L, may be 
automati cally 
accomplished by 
the action of the 
light itself, by 
moving them by 
an electro - mag- Fig. Si5. 

net placed in the circuit of a local battery, and a selenium 
resistance so arranged that when light falls on the selenium 
resistance, the slides L, L, are moved together, and when the 
amount of such light is small, they are moved apart. In this 
way, there is obtained a device roughly resembling the dilata- 
tion or contraction of the pupil of the eye, from the action of 
light on the iris. — (See Photometer, Selenium.) 

Self-Iiiduetioii. — The induction of a current on itself, as 
distinguished from the induction it produces in neighboring 
conductors. (See Currents, Extra.) 

Self'-lndiietioii, Coefficient of A number 

representing the value of the induction produced by a circuit 
on itself, 




544 A DICTIONARY OF ELECTRICAL 

The coefficient of self-induction varies with the shape of the 
circuit, and increases with the number of coils or turns in the 
circuit. The retardation in long telegraph lines, where num- 
erous coils of wire are used, or where there are long cables, is 
due to self-induction as well as to induction in neighboring 
conductors. 

According to Helmholtz, as phrased by Sylvanus Thomp- 
son, " The self induction in a circuit on making contact has 
the effect of diminishing the strength of the current by a 
quantity, the logarithm of whose reciprocal is inversely pro • 
portional to the coefficient of self-induction, and directly 
proportional to the resistance of the circuit, and to the time 
that has elapsed since making the circuit." 

Self-Recording magnetometer. — (See Magneto- 
graph.) 

Self- Winding Clocks.— (See Clocks, Self -Winding.) 

Semaphore. — A variety of signal apparatus employed in 
railroad block systems. 

The semaphore used on the Pennsylvania Railroad consists 
of a wooden post, in the neighborhood of twenty feet in height, 
on which a wooden arm or blade, six feet in length and a foot 
in width is displayed. When the block is clear, the arm is 
placed pointing downwards at an angle of 75* wrth the horizon- 
tal by day, or the semaphore displays a white light at night. 
When the block is not clear, the arm or blade is- placed in a 
horizontal position by day, or displays a red light at night. 
(See Block Signals.) 

Sender, Zinc (See Zinc Sender.) 

Sensibility of Galvanometer .—The readiness and ex- 
tent to which the needle of a galvanometer responds to the 
passage of an electric current through its coils. (See Galvan- 
ometers.) 

Separate Touch, Magnetization by (Sea 

Methods of Magnetization by Touch. Separate. ) 



WORDS, TERMS AND PHRASES. 



545 



Separately Excited Dynamo Electric Machine.— 

A dynamo electric machine, whose field coils are excited by 
means of a source external to the machine. (See Dynamo 
Electric Machine, Separately Excited.) 

Series Circuits. — (See Circuits, Varieties of.) 

Series Connections . — The connection of a number of 
separate electric sources, or electro-receptive devices, or cir- 
cuits so that the current passes successively from the first to 
the last in the circuit. (See Circuits, Varieties of.) 

Series-Multiple Circuit.— (See Circuits, Varieties of.) 



Series, Tlienno-Electric 

Series.) 

Shackle, Telegraphic - 

lation employed on 
a telegraph pole in 
order to confine to 
one point the strain 
caused by a wire 
leaving the insula- 
tor at a sharp angle. 
(See Poles, Tele- 
graphic.) 

Shadow, Elec- 
tric, or Molec- 
ular 



(See Thermo-Electric 



A special form of insu- 




re?. SU6. 
The comparatively dark space on those parts 



of the walls of Crookes' tubes, which have been protected 
from molecular bombardment by suitably placed screens. 

If a, in the Crookes' tube shown in Fig. 346, be connected 
with the negative pole of any electric source, and the cross 
shaped mass of aluminium at b, be connected with the posi- 
tive electrode, on the passage of a series of discharges, phos- 
phorescence is produced by the molecular bombardment from 
a, in all parts of the vessel opposite a, except those lying in 



546 A DICTIONARY OF ELECTRICAL 

the projection of its geometrical shadow. (See Phosphores- 
cence, Electric.) 

Shadow Photometer. — (See Photometer, Shadow.) 

Sheet, Current The sheet into which a current 

spreads when the wires of any source are connected at any 
two points near the middle of a very large and thin conductor. 

A continuous electric current flows through the entire mass 
of a conductor, not in any single line of direction, but, if the 
terminals of any source are connected to neighboring parts of 
a greatly extended thin conductor, the current spreads out in a 
thin sheet known as a current sheet, and instead of flowing in a 
straight line between the points, spreads over the plate in 
curved lines of flow, which, so far as shape is concerned, are 
not unlike the lines of magnetic force. 

Shells, Magnetic (See Magnetic Shells.) 

Shellac. — A resinous substance possessing valuable insul- 
ating properties, which is exuded from the roots and branches 
of certain tropical plants. 

The specific inductive capacity of shellac as compared with 
air is 2.74. 

Shield, Magnetic for Watches.— A hollow case 

of iron, in which a watch is permanently kept, in order to 
seield it from the influence of external magnetic fields. (See 
Magnetic Screens or Shields.) 

Ships, Protection of from Lightning Strokes. 

— (See Lightning Rods for Ships.) 

Ship's Sheathing, Electric Protection of 

— (See Metals, Electric Protection of.) 

Shock, Electric A physiological effect produced 

on animals by the passage through them of an electric cur- 
rent, generally attended by a violent contraction of the 
muscular fibres. 

Short-Circuit . — A shunt, or by-pass, of comparatively 
small resistance, around the poles of an electric source, or 



WORDS, TERMS AND PHRASES. 54T 

around any portion of a circuit, by which so much of the cur- 
rent passes as virtually to cut out any other circuit connected 
therewith, and so prevent it from receiving an appreciable 
current. 
Short-Circuit Key.— (See Key, Short Circuit.) 

Shunt Circuits, Resistance of (See Cir- 
cuits, Shunt, Resistance of.) 

Shunt Circuits, Uses of (See Circuits, 

Shunt, Uses of.) 

Shunt Dynamo, — A dynamo electric machine the field 
magnet coils of which are in a shunt circuit around the ex- 
ternal circuit of the machine. (See Dynamo Electric Ma- 
chine, Shunt.) 

Shunt, *Electro-l?IagTietic In a system of tele- 
graphic communication an electro magnet whose coils are 
placed in a shunt circuit around the terminals of the receiving 
relay. 

The electro-magnetic shunt operates by its self induction. 
Its poles are permanently closed by a soft iron armature, so as 
to reduce the resistance of the magnetic circuit. (See Induction, 
Self.) On making the circuit in the coils of the receiving relay, 
a current is produced in the coils of the electro-magnetic shunt 
in the opposite direction to the relay current, and, on breaking 
the circuit in the relay, a current is produced in the coils of 
the electro-magnetic shunt in the same direction as the cur- 
rent in the receiving relay. The connection of the coils of the 
electro-magnetic shunt with those of the receiving relay, 
however, is such that on making the circuit in the relay the 
current in the shunt coils flows through the relay in the same 
direction, and on breaking the circuit it flows in the opposite 
direction. Therefore this shunt effects the following : 

(1) At the commencement of each signal in the receiving 
relay, it produces an induced current in the same direction 
which strengthens the current in the relay. 



548 A DICTIONARY OF ELECTRICAL 

(2) At the ending- of each signal in the receiving relay, it 
produces a current in the opposite direction, which hastens 
the motion of the tongue of the polarized relay. (See Relay, 
Polarized.) 

Shunt for Galvanometer.— (See Galvanometer Shunt.) 

Shunt or Derived Circuit.— A branch or additional 
circuit provided at any part of a circuit, through which the 
current branches or divides, part flowing through the original 
circuit, and part through the new branch. 

In the case of branched circuits each of the circuits acts as 
a shunt to the others. Any number of additional or shunt 
circuits may be thus provided. (See Kirchhoff's Laws.) 

Shunt, Magnetic An additional path of mag- 
netic material provided in a magnetic circuit for the passage 
of the lines of force. 

Shunts, Multiplying Power of A quantity, 

by which the current flowing through a galvanometer pro- 
vided with a shunt, must be multiplied, in order to give the 
total current. 

The multiplying power of a shunt may be determined from 
the following formula, viz. : 

A = ( S ~^ g ) X C, in which S -+l = the Multiplying Power 

of a Shunt whose resistance is s ; g, is the galvanometer resist- 
ance ; C, the current through the galvanometer; and A, the 
total current passing ; s and g, are taken m ohms, and C and 
A, in amperes. 

Suppose, for example that but 1/10 the entire current is to 
flow through the galvanometer, then the resistance of the 
shunt must evidently be ^ g, for, 

s 1 1 



s + g 1 + 9 10 
or, 10 s = s-f g. 10 s — s=g •'• 9 s = g ; or s= ($) 



WORDS, TERMS AND PHRASES. 549 

Sidero-Magnetic. — A term proposed by Sylvanus P. 
Thompson to replace the word ferro-magnetic. — (See Ferro- 
Magnetic.) 

Siemens and Halske Voltaic Cell.— (See Cell, Voltaic.) 

Signals, Electro Pneumatic Signals operated 

by the movements of diaphragms or pistons moved by com- 
pressed air, the escape of which is controlled electrically. 

Signaling, Velocity of Transmission of 

The speed or rate at which successive signals can be sent on any 

line without the retardation producing serious interference. 

(See Retardation of Signals.) 
Silurus electricns.— The electric eel. — (See Electric Eel. 
Silver Bath.— (See Baths, Silver, etc.) 
Simple Magnet. — (See Magnet, Simple.) 
Simple Voltaic Cell.— (See Cell, Voltaic.) 
Sine Galvanometer.— (See Galvanometer, Sine.) 
Single Fluid Cell. — A voltaic cell in which both elements 

of the couple are immersed in the same electrolyte. (See 

Cell, Voltaic Single Fluid.) 

Single Fluid Electrical Hypothesis. — A hypothesis 
framed to explain the phenomena of electricity on the as- 
sumption of a single electric fluid possessed by all matter. 
(See Electricity, Single Fluid Hypothesis of.) 

Single Touch. — A method of magnetization in which the 
magnetizing bar is merely drawn from one end to the other 
of the bar to be magnetized, and returned through the air for 
the next stroke. (See Magnetization, Methods of.) 
Sinistrorsal Solenoid. — (See Solenoid, Sinistrorsal.) 
Sinuous Currents. — (See Currents, Sinuous.) 
Siphon Recorder. — (See Recorder, Siphon.) 
Skin, Faradization of The therapeutic treat- 
ment of the skin by a faradic current. 



550 A DICTIONARY OF ELECTRICAL 

For efficient faradization the skin should be thoroughly dried 
and a metallic brush or electrode employed. For very sensi- 
tive parts, as, for example, the face, the hand of the oper- 
ator, first thoroughly dried, is to be preferred as an electrode. 

Skin, Human, Electric Resistance of 



The electric resistance offered by the skin of the human body. 

The electric resistance of the skin is subject to marked dif- 
ferences in different parts of the body, where its thickness or 
continuity varies. It varies still more with variations in its 
condition of moisture. Even in the same individual the 
resistance varies materially under apparently similar con- 
ditions. 

Sled. — The sliding contacts drawn after a moving electric 
railway car through the slotted underground conduit con- 
taining the wires or conductors from which the driving cur- 
rent is taken. 

Slide Balance, Wheats tone's. —(See Balance, Wheat- 
stone's Electric.) 

Smee's Voltaic Cell.— (See Cell, Voltaic.) 

Socket, Electric Lamp A support for the re- 
ception of an incandescent electric lamp. 

Incandescent lamp sockets are generally made so that the 
mere insertion of the base of the lamp in the socket completes 
the connection of the lamp terminals with terminals of the 
socket connected with the leads that supply current to the 
lamp, and its removal from the socket, automatically breaks 
such circuit. The socket is generally provided with a key for 
turning the lamp on or off without removing it from the socket. 

Figs. 347 and 348, show forms of lamp sockets for incan- 
descent lamps and the details of the key for connecting or dis- 
connecting the lamp with the leads. 

Soldering, Electric The uniting of metals to 

one another, in which heat generaterd by the electric current 
is used to melt the solder in the place of ordinary heat. 



WORDS, TERMS AND PHRASES. 



551 



-(See Solenoid Prac- 



Solenoid, Dcxtrorsal 

tical.) 

Solenoid, Ideal A solenoid consisting of a 

cylinder built up of true circular currents, with all their faces 
of like polarity turned in the same direction and entirely in- 
dependent of one another. 

The practical solenoid differs from the ideal solenoid in that 
the successive circular circuits or currents are all connected 
with one another in series. 





Fig. 3U7. 



Fig. SIS. 



Solenoid or Helix. Electro-Magnetic Solenoid. 

— The name given to a cylindrical coil of wire, each of the 
convolutions of which is circular. 

A circuit bent in the form of a helix, supported at its two 
extremities, as shown in Fig. 349, and traversed by an elec- 
tric current, will move into the magnetic meridian of the 
place, and if free to move in a vertical plane, will come to 
rest in the line of the dip of the place. 

A solenoid traversed by an electric current acquires thereby 
all the properties of a magnet, and is attracted and repelled 
by other magnets. Its poles are situated at the ends of the 
cylinder on which the solenoid may be supposed to be wound. 



552 



A DICTIONARY OF ELECTRICAL 



The polarity of a solenoid depends on the direction of the 
current as regards the direction in which the solenoid is 
wound. 

This solenoid is sometimes called an electro-magnetic 
solenoid or helix, in order to distinguish it from a mag- 
netic solenoid or solenoidal magnet. (See Magnet, Sole- 
noidal.) 

A solenoid, if suspended so as to be free to move, will come 
to rest in the plane of the magnetic meridian. 

It will also be attracted or repelled by the approach of a 
dissimilar or similar magnet pole respectively, Fig. 351. 



Solenoid, Practical 



— The name applied to 
the ordinary solenoid in 
order to distinguish it 
from the ideal solenoid. 
(See Solenoid, Ideal. ) 

A practical solenoid 
consists, as shown in 
Fig. 350, of a spiral coil 
of wire wrapped in the 
manner shown in the 
figures at (1), (2) and (3.) 

The polarity of the 
solenoid depends on the 
direction of the current, 
and therefore on the 
direction of winding. 
In any solenoid, how- 
ever, the polarity may 
be reversed by revers- 
ing the direction of the 
current. (See Electro- 
Magnet.) 

A Right Handed, or Dextrorsal Solenoid, is one wound in 
the direction shown at (1). 




Fig. 850. 



WORDS, TERMS AND PHRASES. 



553 



A Left Handed, or Sinistrorsal Solenoid, is one wound in 
the direction shown at (2). 

The solenoid shown at (3) is wound so as to produce con- 
sequent poles. (See Consequent Poles, or Points.) 



-(See Solenoid, Prac- 



-A form of induction 



Solenoid, Sinistrorsal 

tical. ) 

Sonometer, Hughes' - 

balance for the purpose 
of examining the inten- 
sity of sounds, or the del- 
icacy of the ear in de- 
tecting or distinguishing 
sounds. (See Induction 
Balance, Hughes.) 

Sonoresce n c e 

A term proposed 

for the sounds produced 
when a piece of vulcanite 
or any other solid sub- 
stance is exposed to a 
rapid succession of flashes 
of light. See Photo- 
phone.) 

Sound (Subjectively) 
The effect pro- 
duced by a vibrating 
body. 

Sound (Objectively). Fig. 351. 

The waves in the air or other medium which produce sound. 

The word sound is therefore used in science in two distinct 
senses, viz. : 

(1.) Subjectively, as the sensation produced by the vibration 
of a sonorous body. 




554 A DICTIONARY OF ELECTRICAL 

(2.) Objectively, as the waves or vibrations that are cap- 
able of producing- the sensation of sound. 

Sound is transmitted from the vibrating body to the ear of 
the hearer by means of alternate to-and-fro motions in the 
air, occurring in every direction around the vibrating body 
and forming spherical waves called waves of condensation 
and rarefaction. Unlike light and heat, these waves require 
a tangible medium such as air, to transmit them. 

Sound, therefore, is not propagated in a vacuum. The vibra- 
tions of sound are longitudinal, that is, the to-and-fro motions 
occur in the same direction as that in which the sound is 
traveling. The vibrations of light are transverse, that is, the 
to-and-fro motions are at right angles to the direction in 
which the light is traveling. 

Sound, Characteristics of (See Character- 
istics of Sound.) 

Sounder, Morse Telegraphic —An 

electro-magnet which produces audible sounds by the move- 
ments of a lever attached to the armature of the magnet. 

The Morse sounder has now almost entirely supplanted the 
paper recorder or register. On short lines it is placed directly 
in the telegraphic circuit. On long lines it is operated by a 
local battery, thrown into or out of action by the relay. (See 
Relay.) 

The Morse sounder, shown in Fig. 352, consists of an upright 
electro magnet M, whose soft iron armature A is rigidly at- 
tached to the striking lever B, working in adjustable screw 
pivots as shown. The free end of the lever is limited in its 
strokes by two set screws N, N. The lower of these screws 
is set so as to limit the approach of the armature A to the poles 
of the electro magnet ; the upper screw is set so as to give the 
end B, sufficient play to produce a loud sound. A retractile 
spring, attached to the striking lever near its pivoted end, and 
provided with regulating screw S S, pulls the lever back when 
the current ceases to flow through M. 



WJRDS, TERMS AND PiiKASUS. 



555 



The dots and dashes of the Morse alphabet are reproduced 
by the sounder, as audible signals, that are distinguished by 
the operator by means of the different sounds produced by the 
up and down stroke of the lever as well as by the difference 
in the intervals of time between the successive signals. 

Sound*, Magnetic — (See Magnetic Sounds.) 

Source, Electric— Anything which produces a difference 
of potential or an electro-motive force. 
Spark Discharge.— (See Discharge, Disruptive.) 
Spark, Length of (See Length of Spark.) 




Fig. 352. 

Spark Tube.— A high vacuum tube, across which the 
spark from an induction coil will not pass, when the vacuum 
is sufficiently high. 

A spark tube, connected with incandescent lamps which 
are undergoing exhaustion, acts as a simple gauge to deter- 
mine the degree of exhaustion. When an induction coil dis- 
charge ceases to pass, or to freely pass, the vacuum is con- 
sidered as sufficient, according to circumstances. 

Sparking of Dynamo-Electric Machines.— An ir- 
regular and injurious action at the commutator of a dynamo- 



556 A DICTIONARY OF ELECTRICAL 

electric machine, attended with spark at the collecting 
brushes. 

Sparking consists in the formation of small arcs under the 
collecting brushes. One cause of sparking is to be found in 
the brushes leaving one commutator strip before making con- 
nection with the next strip. Sparking causes a burning of the 
commutator strips, and an irregular consumption of the 
brushes, both of which produce further irregularities by wear 
or friction of the brushes against the commutator bars. 
Sparking from this cause may be avoided by so placing the 
brush as to cause it to bridge over the space between two 
consecutive bars, thus permitting it to touch one bar before 
leaving the other. Two brushes, electrically connected, are 
sometimes employed for this purpose, or the slots between 
contiguous bars are slightly inclined to the axis of rotation. 

At the moment the brush touches two contiguous commuta- 
tor bars, it short circuits the coil terminating at those bars. 
On the breaking of this closed circuit, a spark appears under 
the brushes. This spark is often considerable, since from the 
comparatively small resistance of the coil, it is apt, when 
short-circuited to produce a heavy current. 

Another cause of sparking is to be found in the self-induc- 
tion of the armature coils. The extra current on breaking 
forms an injurious spark under the brushes. This spark may 
be considerable since the current produced in the coil on mo- 
mentarily short-circuiting it by the brushes simultaneously 
touching the adjoining commutator segments may be large, 

Sparking occurs when the brushes are not set close to the 
neutral line. Since the principal cause for this change in the 
lead of the brushes is the magnetizing effect of the armature 
coils, it is preferable to make the number of windings of these 
as few as possible and to obtain the necessary differences of 
potential by increasing the speed of rotation and the strength 
of the magnetic field of the machine. Short armature coils 
also lessen the sparking due to self-induction. 



WORDS, TERMS AND PHRASES, 557 

Sparking at the brushes is also caused by the jumping of 
improperly supported or constructed brushes. 

"When the brushes are not set close to the neutral point long 
flashing sparks are apt to occur. 

A lack of symmetry of winding of the armature coils will 
necessarily be attended by injurious flashing, from the impos- 
sibility of properly adjusting the brushes. 

Specific Heat.— (See Heat, Specific.) 

Specific Heat of Electricity.— A term proposed by Sir 
Wm. Thomson to indicate the analogies between the absorp- 
tion and emisssion of heat in purely thermal phenomena, and 
the absorption and emission of heat in thermo electric phe- 
nomena. 

As we have already seen heat is either given out or absorbed, 
when an electric current passes from one metal to another 
across a junction between them. (See Effect, Peltier.) 

Co, too, when electricity passes through an unequalh T heated 
wire the current tends to increase or decrease the differences 
of temperature, according to the direction in which it flows, 
and according to the character of the metal. (See Effect, 
Thomson.) 

"If electricity were a fluid," says Maxwell, "running 
through the conductor as water does through a tube, and 
always giving out or absorbing heat till its temperature is 
that of the conductor, then in passing from hot to cold it would 
give out heat, and in passing from cold to hot it would absorb 
heat, and the amount of this heat would depend on the spe- 
cific heat of the fluid." 

Specific Inductive Capacity.— (See Capacit y, Specific 
Inductive.) 

Specific Resi§tance. — (See Resistance, Specific.) 

Specific Resistance of Liquids.— (See Liquids, Spe- 
cific Resistance of.) 

Speecli, Articulate. (See Articulate Speech.) 



558 A DICTIONARY OF ELECTRICAL 

Sphygmograph. — An electric apparatus for obtaining a 
record of the rate and strength of the pulse. 

Sphygmophone.— An applicatoin of the microphone 
to the medical examination of the pulse. (See Microphone.) 

Spiral, Roget's A suspended wire spiral convey- 
ing a strong electric current, and devised to show the attrac- 
tions produced by parallel currents flowing in the same direc- 
tion. 

The lower end of the wire spiral dips into a mercury cup. 
On the passage of the current, the attraction of the neighboring 
turns of the spiral for each other shortens the length of the 
spiral sufficiently to draw it out of the mercury and thus break 
the circuit. When this occurs the weight of the spiral causes 
it to fall and again re-establish the circuit. A rapid automatic 
make-and-break is thus established, accompanied by a bril- 
liant spark at the mercury surface due to the extra spark on 
breaking. 

Split Battery.— (See Battery, Split.) 

Spring- Jack. — A device for readily inserting a loop in a 
main electric circuit. (See Board, Multiple Switch.) 

Spring- Jack Cut-Out, — A device similar in general con- 
struction to a spring jack, but employed to cut out a circuit. 

An insulated plug is thrust between spring contacts, thus 
breaking the circuit by forcing them apart. 

Spurious Resistance. — A false resistance arising from 
the development of a counter electro-motive force. (See 
Counter Electro-Motive Force.) 

Standard Candle. — (See Candle, Standard.) 

Standard Carcel Gas Jet. — (See Car eel Standard Gas 
Jet.) 

Standard Cell. — A voltaic cell the electro-motive force 
of which is constant, and which, therefore, may be used in the 
measurement of an unknown electro-motive force. 



WORDS, TERMS AND PHRASES. 



559 



Absolute constancy is impossible to attain, but, if the current 
of the standard cell is closed but for a short time the electro- 
motive force may be regarded as invariable. 

Standard Cell, Clark's The form of standard 

cell shown in Fig-. 353. 

Latimer Clark's Standard Cell, assumes a variety of forms. 
The H-form is arranged as shown in Fig. 353. The vesse^ 
to the left contains at A an amalgam 
of pure zinc. The other vessel contains 
at M mercury covered with pure mer- 
curous sulphate. Both vessels are then 
filled above the level of the cross tube, 
with a saturated solution of zinc sul- 
phate Z, Z, to which a few crystals of 
the same are added. Tightly fitting 
corks C, C, prevent loss by evaporation. 

The value of this cell in legal volts is 
1.438(1 — 0.00077 (t — 15° C.) (Ayrton.) 

The value t, is the temperature in 
degrees of the centigrade scale. 



Standard Cell, Fleming's 




Fig. 353. 



-The form of standard cell shown in Fie:. 354. 



The U tube, Fig. 354, is connected, as shown, by means of 
taps, with two vessels filled with chemically pure solutions 
of copper sulphate of Sp. Gr. 1.1 at 15° C, and zinc sulphate 
of Sp. Gr. 1.4 at 15° C. respectively. To use the cell the zinc 
rod Zn, connected with a wire passing through a rubber 
stopper is placed in the left hand branch. The tap A is opened 
and the entire U-tube is filled with the denser zinc sul- 
phate solution. The tap at C is then opened, and the 
liquid in the right hand branch above the tap is discharged 
into the lower vessel, but, from this part only. The 
•tap C is then closed, and the tap B opened, and the lighter 
copper sulphate allowed to fill the right hand branch above the 
tap C. The copper rod Cu, fitted to a rubber stopper and con- 



560 



A DICTIONARY OF ELECTRICAL 



nected with a conducting- wire, is then placed in the copper 

solution. 
Tubes are provided at L and M, for the reception of the zinc 

and copper tubes when not in use. The copper tube is 

prepared for use by freshly elec- 
tro-plating it with copper. The 
E. M. F. of this cell is 1.074 
volts. If the line of demar- 
cation between the two liquids 
is not sharp, the arms of the 
vessels are emptied, and fresh 
liquid is run in. 

Standard Resistance 
Coil. — (See Resistance Coil, 
Standard.) 

State, inotropic 

— (See Allotropy.) 

State, Nascent 

(See Nascent State.) 




State, Passive 



of 



Iron. — (See Passive State.) 
State, Permanent 



Fig. 35U. 

State, Variable 



The condition of the charge 
of a telegraph wire when the 
current reaching the distant end 
has the same strength as at the 
sending end. 
-The condition of the charge of 
a telegraph wire while the strength of current is increasing 
up to the full strength in all parts. 

The duration of the variable state is directly as the length 
of the line and its total resistance. It is increased by leakage, 
and by the effect of the extra current. (See Currents, Ex- 
tra.) 



WORDS, TERMS AND PHRASES. 561 

Static Charge.— (See Charge, Static.) 

Static Electricity. — A term formerly applied to electri- 
city produced by friction. (Now obsolete.) 

The term static electricity is properly employed in the sense 
of a static charge but not as static electricity, since that would 
indicate a particular kind of electricity, and, as is now gen- 
erally recognized, electricity, from no matter what source it 
is derived, is one and the same thing. 

Statics. — The science which treats of the relations that 
must exist between the points of application of forces and 
their direction and intensity, in order that equilibrium may 
result. 

Stay Rods, Telegraphic Metallic rods, 

attached to a telegraph pole, and securely fastened in the 
ground in order to counteract the effects of a pull or tension 
on the poles. (See Poles, Telegraphic.) 

Steel, Qualities of Requisite for Magnetiza- 
tion. — Qualities which must be possessed by steel in order to 
permit it to permanently retain a considerable magnetization. 

For the purposes of magnetization steel should possess the 
following qualities: 

It should be hard, and fine grained. Hard cast steel answers 
the purpose very well. Scoresby showed that an intimate 
relation exists between the quality of the iron from which the 
steel is made, and its ability to take and retain considerable 
magnetism. 

An admixture to steel of about .03 per cent, of tungsten 
is said to increase its magnetic powers. Cast steel is not 
generally employed for magnets, wrought steel being gen- 
erally preferred. 

St. Elmo's Fire. — Faintly luminous globes, due to elec- 
tric brush discharges, sometimes seen on the ends of a ship's 
masts, or other similar locations. 



562 



A DICTIONARY OF ELECTRICAL 



Step-oy-Step or Dial Telegraphy.— A system of 
telegraphy in which the signals are registered by the move- 
ments of a needle over a dial on which the letters of the alpha- 
bet, etc., are marked, 

Dial telegraphs are employed for communication by those 
who are unable to readily read the Morse characters. 

The annexed instrument, devised by Breguet, was formerly 
used on some of the railway systems of France. 




Fig. 355. 



Fig. 856. 



A needle advances over a dial in one direction only by a step- 
by-step movement. The alternate to-and-fro motions of the 
armature of an electro magnet are employed to impart a step- 
by-step motion to a peculiarly shaped toothed wheel T, T, Fig. 
355, through the action of a horizontal arm c, attached there- 
to, and moving between the two prongs of a fork d, vibrating 
on a horizontal axis to which is attached a vertical pallet i. 

The receiving instrument is called the Indicator, and con- 
sists of a needle attached to the axis of this wheel. The 
needle moves over the face of the dial, shown in the Fig. 356, 
on which are marked the letters of the alohabet and the nu- 
merals. 

The sending instrument is called the Manipulator. It con- 



WORDS, TERMS AND PHRASES. 



563 



sists of a device for readily sending- over the line the number 
of successive impulses required to move the needle step-by- 
step from any letter on the indicator ,to which it may be point- 
ing, to the next it is desired to send. The dial, shown in Fig. 
357. is marked on its face with the same characters as the in- 
dicator. The edge of the wheel is provided with twenty-six 
notches in which a pin attached to a movable arm engages. 
This arm is jointed so that it can be placed in any of the 
notches on the face ot the wheel. 




Fig. 357. 



Below the dial face, and attached to the same axis as the 
movable arm, is a wheel provided with undulations consisting 
of thirteen elevations and thirteen depressions. 

A lever T, pivoted at a, rests in these undulations at its 
upper end, and plays between two contact points at P and Q. 

If, now. the dials of the indicator and the manipulator both 
being at o, a movement is given to the arm by the handle M, 



564 A DICTIONARY OF ELECTRICAL 

to any point on the manipulator, there are thus produced the 
required number of makes and breaks to move the needle of 
the indicator to the corresponding 1 letter or character. 

Step-toy-Step Telegraphy.— (See Telegraphy, Step-by- 
Step.) 

Stool, Insulating. — A stool, provided with insulating 
supports of vulcanite or other insulator, employed to afford a 
ready insulating stand or support. (See Insulating Stool.) 

Storage Cell§, or Accumulators. — Two inert plates 
of metal, or of metallic oxides, immersed in an electrolyte in- 
capable of acting on them until after an electric current has 
been passed through the liquid from one plate to the other. 

On the passage of an electric current through the electro- 
lyte, its decomposition is effected and the electro positive and 
electro negative radicals are deposited on the plates, or unite 
with them, so that on the cessation of the charging current, 
there remains a voltaic cell capable of generating an electric 
current. 

A storage cell is charged by the passage through the liquid 
from one plate to the other of an electric current, derived 
from any external source. The charging current produces an 
electrolytic decomposition of the inert liquid between the 
plates, depositing the electro positive radicals, or kathions, on 
the plate connected with the negative terminal of the source, 
and the electro negative radicals, or anions, on the plate con- 
nected with the positive terminal. 

On tbe cessation of the charging current, and the connec- 
tion of the charged plates by a conductor outside the liquid 
a current is produced, which flows through the liquid from 
the plate covered with the electro positive radical, to that 
covered with the electro negative radical, or in the opposite 
direction to that of the charging current. 

The simplest storage cell is Plante's cell, which, as origin- 
ally constructed, consists of two plates of lead immersed in 
dilute sulphuric acid, Hg S0 4 . On the passage of the charg- 



WORDS, TERMS AND PHRASES. 



565 



ing current, the plates A and B, Fig. 358, dipped in H 2 S0 4 , 
are covered respectively with lead peroxide Pb 2 , and finely 
divided, spongy lead The peroxide is formed on the positive 
plate, and the metallic lead on the negative plate. 

When the charging current ceases to pass, the cell dis- 
charges m the opposite direction, viz., from B' to A', that is, 
from the spongy lead plate to the peroxide plate, as shown in 
Fig. 359. 




\ 



<? 



\ 


A' B 


i 




-■? -^ 






: 2?^=^=i: 




^z£] 


Q ;— ^=^l-=; 


^f= 


=r~- 


-™ — ^F 




— 






— ■ - 










^— - 











TTTTTT 



Fig. 358. 



Discharging 
Fig. 359. 



As a result of this discharging current the peroxide, Pb 2 , 
on A', gives up one of its atoms of oxygen to the spongy lead 
on B', thus leaving both plates coated with a layer of Pb O, 
lead monoxide, or litharge. When this change is thoroughly 
effected, the cell becomes inert, and will furnish no further 
current until again charged by the passage of a current from 
some external source. 

In order to increase the capacity of the storage cells, and thus 
prolong the time of their discharge, the coating of lead 
monoxide thus left on each of the plates, when neutral, is 
made as great as possible. To effect this, a process called 
forming the plates is employed, which consists in first charg- 
ing the plates as already described, and then reversing the 



566 



A DICTIONARY OF ELECTRICAL 



direction of the charging' current, the currents being sent 
through the cell in alternately opposite directions, until a con- 
siderable depth of the lead plates has been acted on. 

It will be noticed that during the action of the charging 
current, the oxygen is transferred from the Pb0 2 , on one plate, 
to the Pb O on the other plate, thus leaving one Pb, and the 
other Pb 2 ; and that on discharging, one atom of oxygen 
is transferred from the Pb 2 , to the Pb, thus leaving both 
plates covered with Pb O. In reality this is but the final result 
of the action, hydrated sulphate of lead, PbO, H 2 S0 4 , being 
formed, and subsequently decomposed. 

In order to decrease the time required for forming, accu- 
mulators or secondary cells have been constructed, in which 
metallic plates covered with red lead Pb 8 4 , replace the 
lead plates in the original Plante cell. On charging, the Pb 3 
4 , is peroxidized at the anode, i. e., converted into Pb 2 ,and 
deoxidized, and subsequently converted into metallic lead at 
the kathode. Or, in place of the above Pb 3 4 , red lead was 
placed on the anode and Pb O, or litharge on the kathode. 

Plates of compressed litharge have also been recently used 
for this purpose. Storage cells so formed have a greater stor- 
age capacity per unit weight than those in which a grid is 
employed. 

In all such cases, various irregularities of surface are given to 
the plates, in order to increase their extent of surface and to 
afford a means for preventing the separation of the coatings. 
The metallic form thus provided is known technically as a grid. 

Unless care is exercised, the plates will buckle from the dif- 
ference in the expansion of the lead and its filling of oxide. 
This buckling is attended with an increase in the resistance of 
the cell and the gradual separation of the oxides that cover 
or fill it. 

Storage of Electricity. — A term improperly employed 
to indicate such a storage of energy as will enable it to directly 
reproduce electric energy. 



WORDS, TERMS AND PHRASES. 567 

A so-called storage battery does not store electricity, any 
more than the spring- of a clock can be said to store time or 
sound. The spring stores muscular energy, i. e., renders the 
muscular kinetic energy, potential, which, again becoming 
kinetic, causes the works of the clock to move and strike. 

In the same way in a so-called storage battery, the energy 
of an electric current is caused to produce electrolytic decom- 
positions of such a nature as to independently produce a cur- 
rent on the removal of the electrolyzing current. (See Stoi*- 
age Cells.) 

Storms, Electric or Magnetic (See Magnetic 

Storms.) 

Storms, Tli 11 nd it Geographical Distribu- 
tion of. — The following general facts as to the geographi- 
cal distribution of thunder storms, show the intimate relation 
between the frequency of thunder storms and the time and 
place of the condensation of vapor. 

(1) Thunder storms seldom, if ever, occur in the polar 
regions. This is probably because the rain fall here results 
from the condensation of the vapor at times and in regions 
remote from the times and regions in which it was formed. 

(2) Thunder storms seldom, if ever, occur in rainless districts 
owing probably to the absence of the condensation of vapor. 

(3) Thunder storms are most frequent and violent in the 
equatorial regions, where the rain fall results from the con- 
densation of the vapor by the action of ascending currents, 
conveying the vapor almost immediately after its formation 
into the upper and colder regions of the atmosphere. 

(4) Thunder storms occur in regions beyond the tropics, at 
those seasons of the year when the rain fall results from the 
condensation of the vapor shortly after the time of its for- 
mation, viz., in the temperate zones in the hotter parts of the 
year. 

Strain. — The deformation of a body under the influence of 
a stress. (See St7'ess.) 



568 A DICTIONARY OF ELECTRICAL 

strain. Dielectric (See Dielectric Strain.) 

Strain, Electro - magnetic, Optical (See 

Optical Strain, Electro-Magnetic.) 

Strain, Electrostatic, Optical "See Optical 

Strain, Electrostatic.) 

Strain, Optical (See Optical Strain.) 

Stratification Tube.— An exhausted glass tube, the 
residual atmosphere of which displays alternate dark and 
light stria?, or stratifications, on the passage through it of 
an induction coil discharge. (See Luminous Effects of Dis- 
charge.) 

Stray Power.— A term used to indicate the power lost in 
driving a dynamo-electric machine, through friction, air 
churning or currents, and eddy currents. 
Strength of Current.— (See Current, Strength.) 
Strength of Magnetism.— (See Magnetism, Intensity 
of.) 

Stress. — The pressure or pull producing a deformation or 
strain. (See Strain.) 

Stress, Electrostatic, or Electro-Magnetic 

— (See Optical Strain.) 

Striae. Electric (See Stratification Tubes.) 

Struts for Telegraphic Poles.— Inclined wooden or 
iron poles, applied to telegraph poles in order to remove the 
thrust or pressure acting on them. (See Poles, Telegraphic.) 
Sturgeon's Wheel. — (See Accumulator. Barlow's 
Wheel.) 
Submarine Boats. — (See Boats, Submarine.) 
Submarine Cables. — (See Cables, Submarine.) 
Submarine Mines. — (See Mines, Submarine.) 

Submarine Telegraphy (See Telegraphy, 

Systems of. ) 



WORDS, TERMS AND PHRASES. 569 

Substance, Ferro-Magnetic. — (See Ferro-Magnetic 
Substance. 

Subway, Electric An accessible underground 

way or passage provided for the reception of electric wires 
or cables. 

Underground electric conductors like all electric conduc- 
tors are liable to faults, crosses, etc., etc. Unless they are 
readily accessible very serious loss and damage may occur 
before the fault is located and corrected. 

Sun Spots. — Dark spots, varying in number and position, 
which appear on the face of the sun, and are believed to be 
caused by huge vortex motions in the masses of glowing gas 
that surround the sun's body. 

Sun spots occur in greater number at intervals of about 
every eleven years. 

Their occurrence is generally attended with unusual terres- 
trial magnetic variations. (See Magnetic Storms.) 

Sunstroke, Electric or Electric Prostra- 
tion, or Insolation. — Physiological effects, similar to those 
produced by exposure to the sun, experienced by those ex- 
posed for a long while to the intense light and heat of the 
voltaic arc. 

These effects were first noticed by Desprez in his classic ex- 
periments on the fusion or volatilization of carbon. The eyes 
are irritated and the skin burned as by the sun. In some cases 
it is claimed that the effects of sunstroke, or excessive produc- 
tion of heat, as in true insolation, are produced. In the more 
modern application of electricity to electric furnaces, these 
same effects have been noticed in an intensified degree. 

From some recent investigations it would appear that these 
effects are to be ascribed to the light rather than to the heat. 

The symptoms are as follows : Pain in the throat, face and 
temples, followed by a coppery red color of the skin, irritation 
and watering of the eyes, when the symptoms disappear. 
The skin peels off in about five days. 



570 A DICTIONARY OF ELECTRICAL 

Surfaces, Equipotential Electrostatic 

(See Equipotential Surfaces, Electrostatic.) 

Surfaces, Equipotential Magnetic (See 

Equipotential Surfaces, Magnetic.) 

Susceptibility, magnetic A term ex- 
pressing the ratio existing between the intensity of the 
induced and the inducing magnetism. 

The magnetic susceptibility of a bar of iron is equal to the 
intensity of the induced magnetism divided by the strength 
the inducing field. 

Suspension, Bi-Filar The suspension of a 

needle by two parallel wires or fibres, as distinguished from a 
suspension by a single wire or fibre. (See Bi-Filar Suspen- 
sion.) 

Suspension, Combined Fibre and Spring 

— The suspension of a needle by the combined use of a spiral 
spring and a single fibre. 

In this form of suspension the spring is introduced between 
the fibre and the needle. It is valuable for marine galvano- 
meters, and other apparatus exposed to tilting or rolling 
motions, because it permits the instrument to be tilted 
through several degrees without causing any considerable 
variation in the deflections produced by the current or the 
charge. 

Suspension, Fibre Suspension of a needle by 

means of a fibre of unspun silk or other material. 

A fibre suspension generally means a single fibre or thread. 
It may, however, be applied to a bi-filar suspension. (See 
Suspension, Bi-Filar.) 

A fibre suspension is to be preferred to a pivot suspension, 
since it introduces far less friction. It has, however, the dis- 
advantage of necessitating levelling screws. 

Suspension, Knife Edge The suspension 



WORDS, TERMS AND PHRASES. 



571 



of a needle on knife edges that are supported on steel or agate 
planes. 

A suspension of this kind is used in the dipping-needle, since 
it permits of freedom of motion in a single vertical plane only. 

Suspension, Pivot Suspension of a needle 

by means of a jewelled cup and a metallic pivot. 

The jewelled cup is placed above the centre of gravity of the 
needle, and is supported on a steel point. As a rule compass 
needles have this variety of support. 




•yJo^ M M 



Fig. 360. 

Switch, Automatic Telephone 



A device for 

transferring the connection of the main line from the call 
bell to the telephone circuit. 

In most telephone circuits, as now arranged, the automatic 
switch, beside transfering the main line from the call bell to 
the telephone circuit, closes the local battery circuit of the 
transmitter on the removal of the telephone from its support- 
ing hook. 

The means whereby this is accomplished are shown in Fig. 
360. On the removal of the telephone from the hook L, 
the lever is pulled upwards by the spring Z, thus closing the 



572 A DICTIONARY OF ELECTRICAL 

contacts 1, 2 and 3, by which the local battery S is closed in 
the circuit of the transmitter, the telephone disconnected 
from the circuit of the call bell M, B, and connected with the 
circuit of the transmitter. On replacing- the telephone on the 
hook L its weight depresses the lever, breaking connection 
with 1, 2 and 3, and establishing connection with the call cir- 
cuit. 

Switch Board. — (See Board, Switch.) 

Switch, Double Pole A switch that makes or 

breaks contact with both poles of the circuit in which it is 
placed. 

Double-pole switches are used in most systems of incan- 
r>' descent lighting in order 

ffEjjgi aration of the circuit from 

^^^^^^B^^S||HBil : S w i I v h, Rever§iii£ 



■"•""" | * m> ~ 1 ~mb... | J T ■■ j=g=g=rte^ 7 reversing the direction of 

^T ZJ" -1 — ^'! '_ ': " ' '- lk ^^^^^P^" the battery current 

Fig. 361. through a galvanometer. 

A simple reversing switch consists of four insulated brass 
segments mounted on a plate of ebonite and furnished with 
openings between them for plug connections. The battery 
terminals are connected to two diagonally opposite segments 
asB and D, Fig. 361, and the leading wires of the galvanometer, 
or other instrument, to the other segments as C and A. If now 
the plugs are placed between B and C, and A and D, the 
battery current flows in one direction. If, however, the plugs 
are placed between A and B, and C and D, the battery cur- 
rent will flow m the opposite direction. 

The battery current is cut off if one plug is removed. In 
practice, however, it is perferable to remove both plugs, so as 
to avoid any current from want of sufficienc insulation. 



WORDS, TERMS AND PHRASES. 573 

Sympathetic Vibrations. — Vibrations set up in bodies 
by sound waves of exactly the same wave length as those 
produced by the vibrating- body. 

The pitch or tone of the note produced by the body set into 
sympathetic vibration, is exactly the same as the pitch or tone 
of the exciting waves or vibrations. 

Synchronism. — The simultaneous occurrence of any wo 
events. 

A rotating cylinder, or the movement of one index or trail- 
ing arm, is brought into synchronism with another rotating 
cylinder or another index or trailing arm, not only when the 
two are moving with merely the same speed, but when in 
addition they are simultaneously moving over similar portions 
of their respective paths. 

In the Breguet Step-by-Step or Dial Telegraph (See Step-by- 
Step or Dial Telegraph), the movements of the needle on the 
Indicator, are synchronized with the movements of the needle 
on the Manipulator. In systems of Fac-Simile Telegraphy, the 
movements of the transmitting apparatus are synchronized 
with that of the receiving apparatus. In Delany's Synchro- 
nous Multiplex Telegraph System, the trailing-arm that 
moves over a circular table of contacts at the transmitting 
end, is accurately synchronized with a similar trailing-arm 
moving over a similar table at the receiving end. 

Delany, who was the first to obtain rigorous synchronism 
at the two ends of a telegraphic line hundreds of miles in 
length, accomplises this by the use of La Cour's phonic wheel, 
through the agency of correcting electric impulses, automat- 
ically sent in either direction over the main line, when one 
trailing arm gets a short distance in advance or back of the 
other. 

Synchronous Multiplex Telegraphy. — (See Tele- 
graphy, Synchronous Multiplex.) 

System, Astatic (See Astatic System.) 



574 A DICTIONARY OF ELECTRICAL 

System, Block of Railway Telegraphy.— 

(See Block System for Railways.) 

System, Centimetre-Gramme-Second of 

Measurement. — (See Centimetre- Gramme-Second System 
of Measurement.) 

Systems of Distribution by Alternating Currents. 

— System of electric distribution by the use of alternating 
currents. 

Such a system embraces, 

(1) An Alternating-Current Dynamo-Electric Machine. 

(2) A Conductor or Line Wire having a metallic circuit. 

(3) A number of Converters whose primary coils are placed 
in the circuit of the line wire. 

(4) A number of Electro Receptive Devices placed in the cir- 
cuit of the secondary coil of the converter. — (See Converter or 
Transformer.) 

Systems of Distribution by Constant Currents.— 

Systems for the distribution of electricity by means of constant 
currents. 

Distribution by means of constant currents may be effected 
in a number of ways ; the most important are : 

(1) Distribution with Constant Current or Series Distribu- 
tion. 

(2) Distribution with Constant Potential or Multiple Distri- 
bution. 

In a System of Series Distribution, the electro receptive de- 
vices are placed in the main line in series, so that the electric 
current passes successively through each of them. In such a 
system each device added increases the total resistance of the 
circuit. 

In order therefore to maintain the current strength constant, 
independent of the number of devices added, the electro- 
motive force of the source must increase with each electro- 
receptive device added, and decrease with each electro- recep- 



WORDS, TERMS AND PHRASES. 575 

tive device taken out. If the number of electro-receptive de- 
vices be great, such a circuit is necessarily characterized by a 
comparatively high electro-motive force. 

Since the current passes successively through all the electro- 
receptive devices, an automatic safety device is necessary in 
order to automatically provide a short circuit of comparatively 
low resistance past the faulty device, and thus prevent a 
singie faulty device from invalidating the action of ail other 
devices in the circuit. 

Arc lamps are usually connected to the line circuit in series. 

In a System of Multiple Distribution, the electro-receptive de- 
vices are connected with the main line or leads in multiple-arc, 
or parallel, so that each device added decreases the resistance 
of the circuit. In order, therefore, to maintain a proper 
current through the electro-receptive devices, the mains must 
be kept at a nearly constant difference of potential. The 
electro-receptive devices employed in such a system of dis- 
tribution are generally of high electric resistance, so that the 
introduction or removal of a few of the electro-receptive devices 
will not materially alter the resistance of the whole circuit, 
and will not, therefore, materially affect the remaining lights. 

In this system automatic safety devices, operating by the 
fusion of a readily melted alloy or metal, are provided for the 
purpose of preventing too powerful currents from passing 
through any branch connected with the main conductors or 
leads. — (See Plug, Fusible.) 

Incandescent lamps are generally connected with the main 
conductors or leads in parallel or multiple-arc. 

Distribution of incandescent lamps by series connections is 
sometimes employed. Such lamps are usually of compara- 
tively low resistance, and are provided each with an auto- 
matic cut-out, which establishes a short circuit past the lamp 
on its failure to properly operate. 

During the passage of an electric current through any series 
distribution circuit, energy is expended in different portions of 



576 A DICTIONARY OF ELECTRICAL 

the circuit, in the proportion of the resistance of these parts. 
In any system, economy or distribution necessitates that the 
energy expended in the electro-receptive devices must bear as 
large a proportion as practicable to the energy expended in 
the source and leads. In series distribution, this can readily 
be accomplished even if the resistance of the leads is com- 
paratively high since the total resistance of the circuit in- 
creases with every electro-receptive device added, Compara- 
tively thin wires can therefore be employed, for a very con- 
siderable extent of territory covered, without considerable 'oss. 

In systems of multiple distribution, however, this is impos- 
sible ; for, since every electro-receptive device added de. 
creases the total resistance of the circuit, unless the resistance 
of the leads is correspondingly decreased the economy be- 
comes smaller, unless the resistance of the leads was orig 
mally so low as to be inappreciable as compared with the 
change of resistance. 

In systems of distribution by alternating currents, this is 
avoided by passing a current of but small strength and con- 
siderable difference of potential over a line connecting distant 
stations, and converting this current into a current of large 
strength and small difference of potential where it is required 
for use. 

Tachograph. — An apparatus for recording the number 
of revolutions of a shaft or machine per minute. 

Tachometer, or Speed Indicator.— An apparatus 
for determining the number of revolutions of a shaft or ma- 
chine per minute. 

Various forms of apparatus are employed for this purpose. 

Tachyphore. — A term proposed by Wurtz for a system 
of electric transportation, in which a carriage of magnetic 
material is propelled by the sucking action of solenoids 
placed along the track and energized in succession during the 
passage of the car. 



WORDS, TERMS AND PHRASES. 



577 



Tangent. — One of the trigonometrical functions. (See 
( Trigonometry. ) 

Tangent Galvanometer. — A galvanometer in which 
the current strength passing through the deflecting coil is pro- 
portional to the tangent of the angle of deflection it produces 
in the needle. (See Galvanometer, Tangent.) 

Tangent Scale. — A scale designed for use with a galvano- 
meter, on which the values of the tangents are marked, in- 
stead of equal degrees as ordinarily, thus avoiding the neces- 
sity of finding from tables the tangents corresponding to the 
degrees. 

Such a scale may be constructed as follows: Draw the 
tangent B T, to the circle, Fig. 362, and lay off on it any num- 
ber of equal divisions or parts as, for example, the thirty 
shown in the annexed figure. Connect these parts with the 
centre C, of the circle. The arc of the circle will thus be 




Fig. 362. 
divided into parts proportional to the value of the tangents of 
the angles. These parts are more nearly equal the nearer 
they are to B, and grow smaller and smaller the further they 
are from B. In tangent galvanometers, it is therefore very 
difficult to accurately determine the current strength when 
the deflections of the needle are very large. 

Tape, Insulating A ribbon of flexible material 

impregnated with kerite, okonite, rubber, or suitable insulat- 
ing material employed for insulating wires or electric con- 
ductors at joints, or other exposed places, 



578 A DICTIONARY OP ELECTRICAL 

Sometimes the tape is formed entirely of the above named 
insulating materials. 

Tapper, Double Key.— The key used in systems 

of needle telegraphy to send electric impulses through the line 
in alternately opposite directions as desired. (See Telegraphy, 
Single Needle.) 

Target, Electric A target in which the point 

struck by the ball is automatically registered by electric devices. 

A variety of targets have been devised ; generally, how- 
ever, the target is divided into a number of separate sections, 
provided with circuits of wires on the making or breaking of 
any of which, by the impact of the ball, the section struck 
is automatically indicated on an electric annunciator. 

Teazer, Electric Current A name employed 

by Brush for a field magnet shunt circuit around the external 
circuit of his dynamo-electric plating machine. (See Dynamo- 
Electric Machine, Shunt.) 

Tel- Autograph. — A telegraphic system for the fac-simile 
reproduction of handwriting. 

Tele-Barometer, Electric An electric record- 
ing barometer for indicating and recording barometric or 
other pressure at a distance. 

Telegraph, Electric ■ — An apparatus for the 

electric transmission of signals between stations connected by 
electric conductors. 

Various systems of telegraphy are in common use, all of 
which, however, consist of various forms of the following 
apparatus, viz. : 

(1) Transmitting Apparatus, by means of which electrical 
impulses are sent into the line. 

(2) Receiving Apparatus, by means of which the electric 
impulses are caused to produce visible or audible signals, 
which may, or may not, be permanently recorded. 

(3) A Conducting or Line Wire connecting the two stations. 



WORDS, TERMS AND PHRASES. 579 

(4) Main and Local Batteries for producing the currents 
employed in the transmission and reception of the signals. 

(5) Various Relays and Repeaters, employed on long lines, 
in order to permit additional local batteries to be used to carry 
the electric impulses over longer lines than could otherwise 
be employed. 

Telegraphic Code.— (See Alphabet, Telegraphic.) 
Telegraphic Embosser. — (See Embosser, Telegraphic./ 
Telegraphic Joints. — (See Joints, Telegraphic.) 
Telegraphic Xeedle.— (See Needle, Telegraphic ) 
Telegraphic Switch Board. — A device employed at a 

telegraph station by means of which any one of a number of 

telegraph instruments, in use at that 

station, may be placed in, or removed 

from, any line connected with the 

station. 

In the switch board shown in Fig. 
363, the upper left hand binding post 
is connected to earth ; the four re- 
maining binding posts are connected 
to two separate instruments. The sec- 
ond and third from the top, to one 
instrument, and the fourth and fifth, 
to another instrument. The four posts tg ' 

at the top of the figure are connected to two lines running 
east and west. 

Various connections are made by the insertion of plug keys 
in the various openings. 

Telegraphy, American or Morse System of 




— In the Morse system, as now generally employed in America, 
the transmitting apparatus consists essentially of a telegraphic 
key, by means of which the main line circuit can be readily 
made or broken in accordance with tbe dots and dashes of the 
Morse Alphabet. (See Alphabet, Morse.) 



580 A DICTIONARY OF ELECTRICAL 

A metallic lever A, Fig. 364, is supported on a pivot at G, 
between two set screws D, D, so as to have a slight move- 
ment in a vertical plane. This motion is limited in one direc- 
tion by a stop at C, called the anvil or front contact, and in 
the other direction by a set screw F, which constitutes its 
back stop. The front stop C, is provided with a platinum 
contact or stud, which may be brought into contact with, or 
separated from, a similar stud placed directly opposite it. 
These contacts are connected to the ends of the circuit, so that 




Fig. 36U. 
on the movements of the key, by the hand of the operator 
placed on the insulated head B, the line is closed and broken 
in accordance with the dots and dashes of the Morse alphabet. 
A spring, the pressure of which is regulated by the screw F', 
is provided for the upward movement of the key. A switch 
H, is provided for closing the line when the key is not in use, 
since the system as generally used in the United States the 
line is operated on closed circuit. 

In the Morse system each station is provided with a key, 
relay, sounder or register, and a local battery. The closed 
circuit, connecting one station with another, being broken by 
the opening of the switch H, on the working of the key, so as 



WORDS, TERMS AND PHRASES. 581 

to open and close its contacts, the armature of the relay opens 
or closes the circuit of the local battery and operates the 
sounder or registering apparatus connected therewith. (See 
Sounder, Telegraphic. Registering Apparatus, Telegraphic.) 

Telegraphy, Automatic Apparatus by 

means of which a telegraphic message is automatically trans- 
mitted by the motion of a previously perforated fillet of paper 
containing perforations of the shape and order required to 
form the message to be transmitted. 

The paper passes between two terminals of the main line, 
the circuit of which is completed when the terminals come 
into contact at the perforated parts, and is broken when sepa- 
rated by the paper. 

The advantages of the automatic telegraph arise from the 
fact that since the paper fillets can be prepared beforehand, 
great speed is attained by their aid. In the automatic tele- 
graph some form of registering apparatus is employed. 

Type-printing telegraphs are often used for registering 
apparatus, in which case the impulses required for the trans- 
mission of the different letters are automatically sent into the 
line by the depression of corresponding keys on a suitably 
arranged key -board. 

Telegraphy, Chemieal — (See Recorder, 

Bain's Chemical.) 

Telegraphy, Dial (See Telegraph, Step-by- 

Step.) 

Telegraphy, Double Needle A system of 

needle telegraphy in which two separate and independently 
operated needles are employed. 

This system differs from the single needle system only in 
the fact that two needles, entirely independent of each other 
are mounted side by side, on the same dial, so as to permit 
their simultaneous operation by the right and left hand of the 
operator. Each needle has therefore a separate wire. The 



582 



A DICTIONARY OF ELECTRICAL 



increase in speed of signaling thus obtained is not, however, 
sufficiently great to balance the increased expense of con- 
struction. Single needle instruments, therefore, are preferred 
to those with two needles. 

Telegraphy, Diplex A method of simul- 
taneously sending two messages in the same direction over a 
single wire. 

Telegraphy, Duplex Devices whereby two 

telegraphic messages can be simultaneously transmitted over 
a single wire in opposite directions. 

Various duplex telegraphs have been devised. 

The Bridge Duplex is shown in Fig. 365. The receiving re- 
lay is placed in the cross wire of a Wheatstone's balance. 
(See Balance, Wheastone's Electric.) 






Fig. 365. 

When the ends of this cross wire are at the same potential, 
which will occur when the resistances in the four arms are 
proportionally equal, no current passes. 

The battery is connected through the transmitter K, which 
is arranged so that the battery contact is made before the 
connection of the line to earth is broken, to H, where the 
circuits branch to form the arms of the bridge. Adjustable re- 
sistances A, B, are placed in the two arms of the bridge. The 
line wire L, connected as shown, forms the third arm and a 



Words, terms and phrases. 



583 



rheostat or other adjustable resistance R, connected to a con- 
denser C, as shown, forms the fourth arm. (See Rheostat.) The 
relay M, is placed in the cross wire of the bridge thus formed. 
Small resistances V and W, are placed in the circuit of the 
battery to prevent injurious short-circuiting-. 

A similar disposition of apparatus is provided at the other 
end of the line. If, now, the four resistances at one end are 
suitably adjusted, the relay will not respond to the outgoing 
current ; but, since an earth circuit is employed, it will re- 
spond to the incoming current. The relay at either end, there- 
fore, will only respond to signals from the other end. The 
operator may thus signal the distant station while, at the 
same time, his relay, not being affected by his sending, is in 
readiness to receive signals from the other end. 




Fig. 366. 

, Fac-Simile, or Autographic 



or 



Telegraphy 

Pantelegraphy. — Apparatus whereby a facsimile or copy 
of a chart, diagram, or signature is telegraphically transmitted 
from one station to another. 

Bakewell's Fac-Simile Telegraph, which was one of the first 
devised, consists of two similar metal cylinders c, c', arranged 
at the two ends of a telegraph line L, at M and M', as shown 
in Fig. 366. These cylinders are synchronously rotated and 



584 A DICTIONARY OF ELECTRICAL 

provided with metallic arms or tracers r, r', placed on a 
horizontal screw in the line circuit and moved laterally, over 
the surface of the cylinder on its rotation 

At the transmitting station the chart, writing, or other 
design is traced with varnish, or other non-conducting liquid, 
on the surface of the metallic cylinder, as at M, and a sheet 
of chemically prepared paper, similar to that employed in the 
Bain Chemical System is placed on the surface of the receiv- 
ing cylinder at M'. (See Recorder, Bain's Chemical.) 

The two cylinders being synchronously rotated, the metallic 
tracer breaks the circuit in which it is placed when it moves 
over the non-conducting lines on the cylinder, and thus causes 
corresponding breaks in the otherwise continuous blue spiral 
line traced on the paper-covered surface of M'. 

The telegraph keys at R, R', are used for the purposes of 
ordinary telegraphic communication before or after the record 
is transmitted. 

Caselli's Pan-Telegraph is an improvement on Bakewell's 
Copying Telegraph. Better methods are employed for main- 
taining the synchronism between the transmitting and re- 
ceiving instruments, for which purpose a pendulum, vibrating 
between two electro magnets, is employed. 

Telegraphy, Fire Alarm A system of tele- 
graphy by means of which alarms can be sent to a central 
station, or to the fire engine houses in the district, from call 
boxes placed in the line. 

The alarms are generally sounded by an apparatus similar 
to a district call, so that the pulling back of a lever rotates a 
wheel, by means of which a series of makes and breaks are 
produced, the number and sequence of which, enable the 
receiving stations to locate the particular box from which the 
signal is sent. 

In the case of some buildings, the alarms are automatic, 
and either call for help from the central office, or for the 
watchman in the building, or else turn on a series of water 



WORDS, TERMS AND PHRASES. 585 

faucets or jets, in order to extinguish the fire. In these cases 
thermostats are used. (See Thermostats.) 
Telegraphy, Gray's Harmonic Multiple 



A system for the simultaneous 

transmission of a number of separate and distinct musical 
notes, over a single wire, which separate tones are utilized 
for the simultaneous transmission of an equal number of tele- 
graphic messages. 

The separate tones are thrown into the lines by means 
of tuning forks automatically vibrated by electro-magnets. 
These forks interrupt the circuit of batteries connected with 
the main line at the transmitting end of the line. The com- 
posite tone thus formed, is separated into its component tones by 
receiving electro-magnets called Harmonic Receivers, the arm- 
ature of each of which consist of a steel ribbon or plate tuned 
to one of the separate notes sent into the line. As the com- 
plex or undulatory current passes through the coils of each 
harmonic receiver, that note only affects the particular arma- 
ture that vibrates in unison with its ribbon or reed. The op- 
erator, therefore, at this receiver is in communication only 
with the operator at the key of the circuit that is sending this 
particular note into the line. The same is true of the other 
receivers. 

The Morse alphabet is used in this system, the dots and 
dashes being received as musical tones. In practice it was 
found that there was no difficulty in each operator recognizing 
the particular sound of his own instrument in receiving, 
although many instruments were in the same room. 

Telegraphy, Induction A system for 

telegraphing by induction between moving trains and fixed 
stations on a railroad, by means of impulses transmitted by 
induction between the car and a wire parallel with the 
track. 

In such a system, conducting wires directly connecting the 
stations and the moving trains are thus dispensed with, and 



586 A DICTIONARY OF ELECTRICAL 

the signals are received by means of induction effects pro- 
duced between the moving- train and the fixed station. 

Two systems of inductive telegraphy are in actual use, viz. : 

(1) The Static Induction System of W. W. Smith and 
Edison, and 

(2) The Current or Dynamic Induction System of Wil- 
loughby Smith and Lucius J. Phelps. 

In the System of Static Induction, one of the condensing 
surfaces which receives or produces the charge, consists oi a 
wire placed on the road so as to come as near the top of the 
cars of the moving train as possible. The other condensing 
surface is composed of the metal roofs of the moving cars. 
Each condensing surface is connected to suitable instruments 
and batteries, and to the earth ; the line wire at the fixed 
station being connected to earth through- a ground plate, and 
the metal roof of the cars to earth through the wheels and track. 

Under these circumstances variations in the charge of 
either of the condensing surfaces produce inductive impulses 
that are received by the other surface as telegraphic signals. 

The Morse alphabet is employed, but in place of the or- 
dinary receiver or sounder, a telephone is used. 

In the System of Current Induction, the line wire is placed 
near the track, so as to be parallel with a coil of insulated 
wire placed on the side of the car and which receives the in- 
ductive impulses. The coil of wire on the train is connected 
with instruments and batteries, and forms a metallic circuit. 
The line wire is also connected with suitable batteries and 
receiving and transmitting instruments. 

An induction coil is generally employed since the greater 
and more rapidly varying difference of potential of its second- 
ary wire renders it better suited for producing effects of induc- 
tion. A telephone is employed as a receiver, as in the system 
of static induction. The metallic car roof and the lower 
truss rods have been successfully used as the primary and 
secondary conductors of the induction coil. 



WORDS, TERMS AND PHRASES. 587 

The automatic make and break used for operating- the in- 
duction coil, causes the Morse characters employed in this 
system to be received in the receiving telephone as shrill buz- 
zing sounds. 

The receiving telephones used on the trains have a resist- 
ance of about 1,000 ohms. 




Fig. 367. 

Telegraphy, Multiplex A system of tele- 
graphy for the simultaneous transmission of more than four 
separate messages over a single wire. (See Telegraph, Syn- 
chronous, Multiplex.) 

Telegraphy, Printing A system of tel- 
egraphy in which the messages received are printed on a 
paper fillet. 

In Callahan's Printing Telegraph, two type wheels are 



588 



A DICTIONARY OF ELECTRICAL 



employed, one of which carries letter type and the other 
numerals on its circumference. These printing wheels are 
placed alongside of each other, as shown in Fig. 367, but on 
separate and independent axes. 

The type wheels are moved by a step-by-step device. When 
the proper letter or numeral is reached at the receiving end, 
the printing wheel is stopped, and a paper fillet is pressed 
against its surface. The printing wheel is kept covered with 
ink by means of an inked roller. 





Fig. 368. 

The transmitting instrument is similar in its operation to 
the Breguet Manipulator. Separate transmitters are used 
for each of the wires. (See Telegraphy, Step-by-Step.) 

Telegraphy, <£uadriiplex — - — — A. system for 

the simultaneous telegraphic transmission of four messages 
over a single wire. 



WORDS, TERMS AND PHRASES. 



589 



There are various systems of quadruplex telegraphy. For 
the details of their operation the student is referred to stand- 
ard books on telegraphy. 

Telegraphy, Single Needle ■ —A system of 

telegraphy by means of which the signals transmitted are re- 
ceived by observing the movements of a vertical needle over 

a dial. 

Movements of the top of the needle to the right of the 
observer represent the dashes, and movements to the left, -the 
dots of the Morse alphabet. 




Fig. 370. Fi &- 37L 

The single needle apparatus of Wheatstone and Cooke's 
svstem is shown in Figs. 368 and 369. Fig. 368, shows the 
external appearance, and Fig. 369, the internal arrangements 
as seen from the back. An astatic needle is placed inside two 
coils of insulated wire C C. Only one of these needles N, is 
visible on the face of the receiving instrument. The current 
from the line enters at L, passes through the coil C C, and 
leaves at N. 



590 A DICTIONARY OF ELECTRICAL 

The movements of the needle to the right or the left are ob- 
tained by changing the direction of the current in the coils 
C C. This is effected by working the handle when send- 
ing, and thus moving the commutator at S, S, and bringing 
the contact springs resting thereon into different contacts. 

In the more modern form of Single Needle Instrument, 
shown in Fig. 370, a single magnetic needle N S, Fig. 371, 
only is placed in the coil. 

This needle is rigidly attached to a light needle a, b, used 
only as a pointer, and is alone visible in the front of the figure 
on the left. The relative disposition of these 
needles is shown in the drawing on the right. 

The reversals of the current, required to 
deflect the needle to the right or left, are ob- 
tained by means of a double key or tapper, 
shown in Fig. 372. 
1~] The levers L and E, are connected respect- 
wCm!X^2 ively to line and earth, and, when not in use, 

I , rest against C, connected with the positive 

■ ]|| r 1 I side of the battery ; but when depressed con- 



's nect with Z, attached to the negative side of 

Fiq 872 * ne Dat tery. The depression of L, therefore, 

sends a negative current into the line and 
deflects the needle, say, to the left, while the depression of 
E sends a positive current into the line and deflects the 
needle to the right. The terms positive and negative currents 
are used in telegraphy to indicate currents whose direction is 
positive or negative. 

Telegraphy, Speaking A system for the 

telegraphic transmission of articulate speech. (See Tele- 
phones.) 

Telegraphy, Step-foy-Step A system of 

telegraphy in which the needle of a dial, or the type wheel 
of a printing telegraph, is moved step-by-step by electric 
impulses sent over the line. (See Telegraphy, Needle or Dial.) 



WORDS, TERMS AND PHRASES. 591 

Telegraphy, Sub-Marine A system of 

telegraphy in which the line wire consists of a sub-marine 
cable. 

In long sub-marine cables, in order to avoid retardation 
from the self-induction of the current, and the static charge 
arising from the cable acting as a condenser, very small 
currents are used. To detect these a very sensitive receiv- 
ing instrument, such as the mirror galvanometer, or the 
siphon recorder, is employed. (See Galvanometer, Mirror. 
Recorder, Siphon.) 

According to Culley, the retardation in the case of one of 
the sub-marine cables between Newfoundland and Ireland, 
amounts to two-tenths of a second before a signal sent from 
one end produces any appreciable effect at the other end, 
while three seconds are required for the current through the 
cable to gain its full strength. 

Telegraphy, Synchronous-Multiplex, 

Delany's System. — A system devised by Delany for the 
simultaneous telegraphic transmission of a number of 
messages either all in the same direction, or part in one 
direction and the remainder in the opposite direction. 

The Delany System embraces the following parts : 

(1) A circular table of alternately insulated and grounded 
contacts at either end of a telegraphic line. 

(2) A synchronized rotating arm or trailing contact, at each 
end of the line, driven by a phonic wheel, and maintained in 
synchronous rotation by means of electric impulses automatic- 
ally sent out over the main line in either direction, on the 
failure of the wheel at either end to rotate synchronously with 
that at the other end. 

(3) Transmitting and receiving instruments connecting 
similar contacts at each end of the main line, and forming prac- 
tically separate and independent lines for the simultaneous 
transmission of dispatches over the main line in either direc- 
tion. 



592 A DICTIONARY OF ELECTRICAL 

The main line is simultaneously connected at both of its ends 
to corresponding operating instruments, and transferred from 
one set of instruments to another so rapidly that the operators, 
either sending or receiving, cannot realize that the line has 
been disconnected from their instruments and given to others, 
because each of them will always have the line ready for use, 
even at the highest rate of manipulation, and will, therefore, 
to all practical intents and purposes, have at his disposal a 
private wire between himself and the operator with whom 
he is in communication. 

Therefore, although more than one operator may be spoken 
of as simultaneously using the line at any given time, yet 
in point of fact no two operators are in reality absolutely 
using it at the same time ; but they follow one another at 
such short intervals, and the line is taken from one operator 
and transferred to another so rapidly that none of them can 
at any time tell but that he has the line alone, and that there- 
fore it is practically open for the use of every operator just as 
if he alone had control of it. 

There will, therefore, be established, by the use of a single 
line, as many private and separate lines as there are trans- 
ferences of the line from the time it is taken from the first 
operator, and again given back to him. 

This system has been extended to as many as seventy-two 
distinct and separate printing circuits, maintained and operated 
on a single connecting line wire. 

Fig. 373, shows the apparatus at each end of the line, at the 
stations X and Y. The apparatus at each end is substantially 
identical. A steel fork a, at each station, is automatically 
and continuously vibrated by the action of the local battery 
L B, and the electro-magnet A, called the vibrator magnet. 

Platinum contacts x, xf 1 , placed on the inner faces of the 
tines of the fork, make and break contact with delicate con- 
tact springs y, y 1 . 

The fork being mechanically started into a vibratory mo- 



WORDS, TEEMS AND PHRASES. 



593 



tion, will automatically make and break its local circuit, and 
thus send impulses into the fork-magnet A, that will continu- 
ously maintain the vibrations of the fork, m a well-known 
manner. 

The making and breaking of the contacts x and y, conse- 
quent on the fork's vibration, opens and closes a circuit of an- 
other local battery called the motor circuit, m which is placed 
an electro-magnet D. the function of which is to maintain the 
continuous rotation of the transmission apparatus C, 




^ sk ^n vrn w^ 



Fig. 373. 

The continuous vibration of the fork makes and breaks the 
contacts at x and y, and thereby makes and breaks the motor 
circuit. The alternate magnetizations and demagnetizations 
of the cores of the motor-magnet D cause the rotation of the 
transmission apparatus C. 

The motor-magnet and transmission wheel or disc C, pro- 
vided with projections c, c, is the invention of Paul La Cour, 
and is styled by him a ' Phonic Wheel," 



594 



A DICTIONARY OF ELECTRICAL 



The transmission apparatus is illustrated in detail in Figs. 
374 and 375, and is an exact counterpart of the receiving appar- 
tus at the other end of the line. A base plate E, provided with 




Fig. 37k. 

binding posts, carries a vertical rotary shaft F. A circular 
table F 1 , is provided with a series of insulated contacts ar- 
ranged symmetrically around the axis of rotation of the shaft. 




Fig. 375. 



A radial arm F 2 , connected with the shaft F, carries at its 
outer extremity a trailing contact finger /. As the disc C is 
rotated by the electro-magnet D, the trailing contact f, 



WORDS, TERMS AND PHRASES. 595 

sweeps around the circular table F 1 , and is brought success- 
ively into contact with the insulated contact-pieces placed on 
the upper face of the table F 1 . 

The main line Q. Q, has one of its ends connected with the 
trailing' finger/. As the shaft F, rotates, the line is therefore 
brought into successive electrical connection with the series 
of insulated contacts in the upper face of the table F 1 . 

Any suitable number of insulated contacts may be placed 
on the circular table F 1 ; sixty are shown in Fig. 376 In 
practice these contacts are connected in accordance with the 
number of circuits which it is desired to simultaneously 
maintain on the same wire. In the special case shown 
in the figure referred to above, it is arranged so that 
four separate circuits shall be established on the same line 
wire. The sixty contacts are placed in six independent series, 
numbered from 1 to 10, consecutively. In the arrangement 
here shown two of the contact pieces in each series of ten 
are connected tn the same circuit, and as there are six series, 
each of the circuits so connected will have twelve contacts 
for each rotation of the disc, and twelve electrical impulses, 
as will be afterwards described 

The detailed mechanism by means of which the separate 
and independent circuits so obtained are utilized for the trans- 
mission and reception of messages is shown in Fig. 376. R, 
R 1 , R 2 and R 3 are polarized relays; S, S 1 , S 2 and S 3 are ordi- 
nary Morse sounders, although in the practice of this inven- 
tion some improvement has been introduced in connection 
with the receiving instruments. The connections with the 
main and the local batteries M B and L B, are clearly shown 
in the figure. 

It will be noticed that the relay R is connected with the wire 
r, and with the contacts 1 and 5 ; R 1 , is connected by r 1 , with 
the contacts 2 and 6 ; R 2 , by the wire r 2 , with the contacts 3 
and 7; and R 3 , by the wire r 3 , with the contacts 4 and 8 Sim- 
ilar instruments and circuits are placed at each end of the line. 



596 



A DICTIONARY OF ELECTRICAL 



Without further describing the operation of the instruments 
shown in the figure, it need only now be borne in mind that 
the corresponding relays at the distant stations are connected 
with the correspondingly numbered contacts When, there - 
fore, the trailing contact finger at each station simultaneously 
touches the contacts bearing the same number, the corre- 




Fig. 876 

sponding instruments connected with these contacts at each 
station will be placed in communication over the main line, 
the trailing contact finger /, completing the connection of the 
mam line with the contact arm in the manner already de- 
scribed. 



Telegraphy, Time 

graphic transmission of time. 



-A system for the tele- 



WORDS, TERMS AND PHRASES. 



597 



A system of time-telegraphy includes a master clock, the 
movements of whose pendulum automatically transmit a 
number of electric impulses to a number of secondary docks 
and thus moves them ; or self winding clocks are employed, 
which are corrected daily by an impulse sent over the line 
from a master clock. — (See Clocks, Electric.) 

A o-auo-e for elec 



Tele-Manometer, Electric 

trically indicating and recording pressure at a distance. 




Fig. 381. 
The tele-manometer includes a pressure gauge furnished with 
electric contacts operated by the movements of the needle of 
the steam gauge for instance, and indicating and recording 
apparatus. An alarm bell is provided to call attention to any 
rise of the pressure above, or its fall below the given or pre- 
determined limits for which the hands have been set. 



598 A DICTIONARY OP ELECTRICAL 

Telemeter. — An apparatus for electrically indicating and 
recording at a distance, the pressure on a gauge, the reading 
of a thermometer, or the indications of similar instruments. 
(See Tele-Barometer. Tele-Manometer. Tele-Thermometer.) 

Teleplierage. — A system (Fleeming Jenkin) for the con- 
veyance of carriages suspended from electric conductors, and 
driven by means of electric motors, that take directly from 
the conductors the current required to energize them. 

Two lines are provided, an up and a down line, that cross 
each other at regular intervals. Each line is in segments, and 
the alternate segments are insulated from each other, but are 
connected electrically by cross pieces on the supporting posts. 
In this way the line shown in Fig. 382, is obtained. 



@ - °» f *H5) 



U* 



I ' ■*" *• 

Fig. 882. 

The two lines are maintained at a difference of potential 
by a dynamo-electric machine at D, Fig. 382. As the train at 
L T, or L' T', is of such a length as to come into contact with 
two different segments at the same time, it receives a current 
sufficient to run the motor connected with it, the current being 
received through a conductor joining a pair of wheels that 
are insulated from the truck. 

The general arrangement of the line is shown in the an- 
nexed Fig. 381. 

Telephone. — An apparatus for the electric transmission 
of articulate speech. 

The articulating telephone, though first brought into public 
use by Bell, was invented by Reis, in Germany, in 1861. In 
America, after very protracted litigation, Bell has been decided 



WORDS, TERMS AND PHRASES. 



599 



legally to be the first inventor, but scientific men very gener- 
ally recognize the principles of the invention to be fully an- 
ticipated by the earlier instruments of Eeis. Bell, however, 
is justly entitled to credit for his improvements in the Eeis 
apparatus. 

In Bell's Magneto-Electric Telephone, the transmitting and 
receiving instruments are identical. A coil C, of insulated 
wire connected with the line, is placed on a core of magnetized 
steel, mounted opposite the centre of a 
circular diaphragm of thin sheet iron, 
rigidly supported at its edges. 

In transmitting, the message is spoken 
into the mouth-piece at one end, as at D, 
in Fig. 378, and the to-and-f ro motions thus 
imparted to the metallic diaphragm at- 
tached to the mouth-piece P, produce in- 
duction currents in the coil C, on the 
magnet M. (See Induction, Electro Mag- 
netic.) These impulses, passing over the 
main line E L, produce similar movements 
in the diaphragm P', of the receiving in- 
strument, at D', and thus causes it to repro- 
duce the message, in articulate sounds, to one listening at the 
receiving instrument. A ground circuit is shown in the figure, 
as usually employed in practice. 

A magneto - telephone 
constitutes in reality a 
magneto- electric ma- 
chine, driven or propelled 
by the voice of the speak- 
er, in which the currents 
so produced instead of being commuted are employed uncom- 
muted to reproduce the uttered speech. 

In actual practice this instrument is replaced by the electro- 
magnetic telephone, in which the to-and-fro motions of the 





Fig. 378. 



600 



A DICTIONARY OF ELECTRICAL 



transmitting diaphragm are caused to vary the resistance of a 
button qf carbon, or a variable contact-transmitter similar 
to that employed by Reis in some of his instruments. The 
variable resistance is placed in the circuit of a battery, so 
that on speaking into the transmitter, electric impulses are 
sent over the line and are received by a telephone with a 
magnet core provided with a coil in the main line circuit. 

The telephone is arranged for actual commercial use in the 
United States in the manner shown in Fig. 379. 

Telephone, Electro-Capillary A telephone in 

which the movements of the transmitting 
diaphragm produce currents by means of 
variations in the electro-motive forces of 
the contact surfaces of liquids in capillary 
tubes. (See Electro Capillary Phe- 
nomena.) 

In Breguet's telephone both the trans- 
mitting and the receiving instruments are 
similar in construction and operate by 
means of electro-capillary phenomena. 
A vertical capillary tube communicates 
at its upper end with an air space below 
a diaphragm, and at its lower end with a 
mercury surface on which rests a layer of 
acidulated water. A line wire connects 
Fig. 379. ^he mercury reservoirs of the transmit- 

ting and receiving instruments, the remainder of the circuit 
being formed by another wire connecting the mercury near 
the upper parts of the two vertical tubes. 

The alterations in the contact surfaces at the transmitting 
end produced by the movements of the diaphragm, cause 
electric impulses that produce similar movements of the dia- 
phragm at the receiving end. 

Telephone, Electro-Motographic or Edi- 
son's Electro-Chemical Telephone.— A telephone in 




WORDS, TERMS AND PHRASES. 601 

which the receiver consists of a diaphragm of mica or other 
elastic material operated on the principle of the electro-moto- 
graph. 

A straight lever, which forms part of the line circuit is 
rigidly attached at one end to the centre of the receiving 
diaphragm and rests near its other end on the moistened sur- 
face of a chalk cylinder, maintained in rotation by suitable 
mechanical means. Electric impulses being sent into the line 
by the voice of a speaker talking at a transmitter of ordinary 
construction, produce slipping movements of the cylinder 
that reproduce in the receiving diaphragm articulate speech. 
Telephonic Exchange. — (See Exchange, Telephonic.) 
Telephonic Joints of Wire.— (See Joints, Tele- 
graphic.) 

Telephote or Pherope.— An apparatus for the tele- 
graphic transmission of pictures through the action of light 
on selenium. (See Telephotography.) 

Telephotography. — A system for facsimile transmis- 
sion by means of dots and lines transmitted by means of a 
continuous current whose intensity is varied by a transmitting 
instrument, containing a selenium resistance. (See Tele- 
graph, Fac-Simile. S elenium Resistance.) 

The transmitter consists of a dark box, mounted on an axis, 
so as to be capable of a sidewise motion. The picture to be 
transmitted is thrown continuously on the face of the box by 
any lantern projection apparatus, and a small opening con- 
taining a selenium resistance receives the alternations of 
light and shade, and transmits the same as variations in the 
strength of the otherwise continuous current in the circuit of 
which the selenium resistance is placed. The picture is re- 
ceived at the other end on a sheet of chemically prepared 
paper moved synchronously with the transmitting box. 

Telescope, Reading A telescope employed 

in electric measurements, for reading the deflections of the 
galvanometer. 



602 



A DICTIONARY OP ELECTRICAL 



A mirror, suspended above the needle on the same fibre that 
holds the needle, reflects a spot of light on a scale by which 
the amount of deflection is indicated. (See Galvanometer, 
Mirror.) 

A form of reading telescope is shown in Fig-. 380. An 
illumined scale M, receives the spot of light reflected from the 
mirror attached to the galvanometer suspension, and the 
deflection is observed in the mirror by the telescope F. 

Teleseme.— A self-registering hotel annunciator, by means 
of which a dial operated in a room, indicates on the an- 
nunciator the article or service 
required. 

Tele-Thermometer, Elec- 
tric An electric record- 
ing thermometer for indicating 
and recording temperature at a 
distance. 

Temperature Alarm.— (See 

Alarm, Fire, etc.) 

Temperature, Effects of 
on Electric Resistance. 

— (See Resistance, Effects of Tem- 
perature on.) 

Tension, Electric 

A term often loosely applied to 
signify electro-motive force, dielectric stress, difference of 
potential. 

This term is now very generally abandoned. 

Terrestrial Magnetism. — (See Magnetism Terrestrial.) 

Testing, Methods of (See Measurements, Elec- 
tric.) 

Therm. — A heat-unit recently proposed by the British As- 
sociation. 

A therm is the amount of heat required to raise the temper- 




Fig. 380. 



WORDS, TERMS AND PHRASES. 60S 

ature of one gramme of pure water at the temperature of its 
maximum density one degree centigrade. (See Calorie.) 

Tliermo-EIectric Battery. — (See Battery, Thermo- 
Electric.) 

Tliermo-EIectric Couple. — Two dissimilar metals 
joined so as to produce thermo-electric currents through dif- 
ferences of temperature. 

Tliermo-EIectric Diagram. — (See Diagram, Thermo- 
Electric.) 

Tliermo-EIectric Inversion. — An inversion of the 
thermo-electric power of a couple at certain temperatures 
(See Diagram, Thermo-Electric.) 

Tliermo-Electricity. — Electricity produced by differ- 
ences of temperature at the junctions of dissimilar metals. 

If a bar of anti- 
mony is soldered 
to a bar of bismuth, e====J ^ 
and their free ends 
connected by 
means of a galvan- 
ometer, the appli- 
cation of heat to ~ Fig. 381. 
the junction, so as to raise its temperature above the rest of 
the circuit, will produce a current across the junction from the 
bismuth to the antimony, (against the alphabet, or from B to 
A). If, the junction be cooled below the rest of the circuit, a 
current is produced across the junction from the antimony to 
the bismuth, (with the alphabet, or from A to B). These cur- 
rents are called thermo-electric currents, and are proportional 
to the differences of temperature. 

Even the same metal, in different physical states or condi- 
tions, such as a wire, part of which is straight and the remain- 
der bent into a spiral as at H C, Fig. 381, if heated at F by 
the flame of a lamp will show o> current developed in it. 




A DICTIONARY OF ELECTRICAL 



The same thing may also be shown by placing a cylinder of 
bismuth J, Fig. 382, in a gap in a hollow rectangle of copper 
A B, inside of which a magnetic needle M is supported. 
A 




The rectangle of copper being placed in the magnetic me- 
ridian, on heating the junction by the flame of a lamp F the 
needle will be deflected by a current produced by the differ- 
ence of temperature. 

Thermo-Eleetrie Pile, differential (See 

Differential Thermo-Electric Pile.) 



a + 





Fig. 383. Fig. 38k. 

Thermo-Electric Pile or Battery.— A number of 
separate thermo-electric couples, united in series, so as to 
form a single thermo-electric source. 



WORDS, TERMS AND PHRASES. 



605 



Figs. 383, and 384, show Nobili's Thermo-Pile, in which a 
number of bismuth-antimony thermo-electric couples are con- 
nected in a continuous series, as shown in Fig. 386, and insu- 
lated from one another, except at their junctions, and packed 
in a metallic box, and supported as shown in Fig. 385. The 
free terminals of the series are connected to binding posts. 
Differences of temperature between the two faces of the 
pile, where the junctions are exposed, result in a current 
whose difference of potential is equal to the sum of the differ- 
ences of potential of all the thermo-electric couples. 

A careful inspection of the drawing will show that the junc- 
tions are formed successively at opposite faces of the pile, so 
that if the junctions be numbered successively, the even junc- 
tions will come at one face, and the odd junctions at the 
other. This is necessary in order to permit all the thermo- 
electric couples to add their differences of potential ; for, if, 




Fig. 385. 

as in Fig. 385, a thermo-electric chain be formed, no currents 
will result from equally heating any two consecutive junc- 
tions J J, of the metals A and B, since the electro-motive 
forces so produced oppose each other. 

Thermo piles have been constructed by Clamond of couples 
of iron and an alloy of zinc and antimony, of sufficient power 
to produce a voltaic arc whose illuminating power equalled 
40 carcel burners. Many practical difficulties exist which will 
have to be surmounted before such piles can be employed as 
commercial electric sources, - 



606 A DICTIONARY OF ELECTRICAL 

Tiiermo-EIectric Power.— (See Power, Thermo-Elec- 
tric. ) 

Thermo-Electric Series.— A list of metals so arranged, 
according- to their thermo-electric powers, that each metal in 
the series is electro-positive to any metal lower in the list. 

Thermo - Electro - Motive Force. — Electro - motive 
force, or difference of potential, produced at thermo-electric 
junctions by differences of temperature. 

Thermometer, Electric or Tliermo- 

Electroineter. — A device for determining the effects of an 
electric discharge by the movements of a liquid column on 
the expansion of a confined mass of air through which the 
discharge is passed. 

Thermometer Scale, Centigrade (See Cen- 
tigrade Scale.) 

Thermometer Scale, Fahrenheit (See Fah- 
renheit Scale.) 

Thermophone. — Any instrument by means of which 
sounds are produced by the absorption of radiant energy. 
(See Photophon 

A telephone has been constructed in which the motions of 
the receiving diaphragm are effected by the expansions and 
contractions of a thin metallic wire connected to its centre 
and placed in the circuit of the main line. 
Thermostat. — An instrument for automatically indicat- 
ing the existence of a given tem- 
perature by the closing of an 
electric circuit through the ex- 
pansion of a solid or liquid. 

Thermostats are used in sys- 
tems of automatic fire tele- 
graphy, and in systems of auto- 
es'- s86 ' matic temperature regulation. 
Three- Wire System.— A system of electric distribution, 
invented by Edison, in which three wires are employed, 




WORDS, TERMS AND PHRASES. 607 

In this system three conductors are connected to a source 
of electric energy, Fig. 886, and the difference of potential 
between the central and the two outer conductors is always 
maintained the same. The lamps or other electro-receptive 
devices are placed in multiple arc between either branch, and 
so distributed that the current in each branch is the same. 
When such a balance is established no current flows through 
the central or neutral conductor. But when that balance is 
disturbed the surplus current in one branch is taken up by the 
central conductor. This system effects considerable economy 
in the weight of wire required. 

Thunder. — A loud noise accompanying a lightning dis- 
charge. 

Thunder is due to the sudden rush of the surrounding air to 
fill the vacuous space accompanying the disruptive discharge 
of a cloud. This space is caused by the condensation of the 
vapor formed on the passage of the discharge through drops 
of rain or moisture in the air, as well as by the expansion of 
the air itself. ' 

Thunder-Storms, Geographical Distribution of 

(See Storms, Thunder, Geographical Distribution of .) 

Tick, Magnetic. A faint metallic click heard on 

the magnetization and demagnetization of a magnetizable 
substance. (See Magnetic Tick.)* % 

Time Ball, Electric A ball, supported in a 

prominent position on a tall pole, and caused to fall at the 
exact hour of noon, or at any other predetermined time, for 
the purpose of thus giving the exact time to an entire neigh- 
borhood. 

The release of the ball is effected by the closing of an elec- 
tric circuit, either automatically, or through the agency of an 
observer. 

Time Cut-Outs, Automatic. Automatic 

cut-outs arranged on storage batteries to cut them in or out of 
the circuit of the charging source, at predetermined times, 



608 A DICTIONARY OF ELECTRICAL 

Time Telegraphy.— (See Telegraphy, Time. Clocks, 
Electric.) 

Tongs, Discharging (See Discharging Rods.) 

Top, Induction (See Induction, Top.) 

Torpedo, Electric (See Ray, Electric.) 

Torsion Balance.— (See Balance, Torsion.) 

Torsion Galvanometer.— (See Galvanometer, Torsion.) 

Total or Dead Earth.— (See Earths.) 

Touch, Single, Separate or Double Methods 

of Magnetization by.— (See Magnetization, Methods of.) 
Tourmaline. — A mineral consisting of natural silicates 

and borates of alumina, lime, iron, etc., possessing- pyro- 

electric properties. (See Pyro-Electricity.) 
Tower, Electric. A high tower provided for 

the support of a number of electric arc lamps, employed in 

systems of general illumination. 

Tower, System of Electric Lighting,— The lighting 
of extended areas by means of arc lights placed on the top of 
tall towers. 

The tower-systenl of electric illumination is only applicable 
to wide, open spaces, since otherwise objectionable shadows 
are apt to be formed. 

Train Signaling. — (See Telegraphy, Inductive.) 

Transmission of Energy. — (See Energy, Transmis- 
sion of.) 

Transmitters, Electric Various electric ap- 
paratus employed in transmitting or sending the electric im- 
pulses over a telegraph line. 

In most telegraphic systems, the transmitting apparatus 
consists of various forms of keys for interrupting or varying 
the current. In the telephone the transmitter consists of a 
diaphragm operated by the voice of the speaker. (See Tele- 
graph. Telephone.) 



WORDS, TERMS AND PHRASES. 



609 



Tran§former or Converter. 

Transformer.) 

Treatment, Hydro-Carbon — 



(See Converter or 



of Carbons.- 



(See Flashing Carbons, Process for.) 

Trigonometry. — That branch of mathematical science 
which treats of the methods of determining' the values of the 
angles or sides of a triangle. 

There are in every triangle three sides and three angles. If 
any three of these parts are given, except the three angles, 
the values of the remaining parts can be determined by means 
of trigonometry, by what is called the solution of the triangle. 

Trigonometrical Functions.— Certain quantities, the 
values of which are dependent on the length of the arcs sub- 
tended by angles, which are taken for the measures of the 
arcs instead of the arcs themselves. 

The trigonometrical functions are 
the sine, the co-sine, the tangent, the 
co-tangent, the secant, and the co- 
secant. These are generally abreviat- 
ed, thus, viz. : sin, cos, tan, cot, sec, 
and co-sec. 

The Sine of an angle, or arc, is the 
perpendicular distance from one ex- 
tremity of the arc to the diameter pass- 
ing through the other extremity. 
Thus in Fig. 387, B D, is the sine of 
the angle B O A, or of the arc, B A. 

The Cosine of an angle, or arc, is that part of the diameter 
which lies between the foot of the sine and the centre. Thus 
D O, is the cosine of the angle B O A, or of the arc B A. 

The cosine of an arc is equal to the sine of its complement. 
Thus E O B or B E, the complement of B A, has for its sine 
I B, which is equaL to O D. (See Complement of Angle.) 

than a right angle, or 90°, such, for 




610 A DICTIONARY OF ELECTRICAL 

instance, as the angle TOG, or the arc B E F G, B D is its sine. 
This is also the sine of BOA, or of B A, which is the supple- 
ment of TOG, or B E F G. Hence the sine of an arc is equal 
to the sine of its supplement. 

The same is true of the cosine. 

The Tangent of an angle, or arc, is a straight line touching 
the arc at one extremity, drawn perpendicular to the diameter 
at one end of the arc, and limited by a straight line connect- 
ing the centre of the circle and the other end of the arc. Thus 
C A is the tangent of the angle B O A, or the arc B A. 

The Co-tangent of an angle, or arc, is equal to the tangent of 
its complement, thus E T, is the co-tangent of the angle, 
B O A, or the arc B A. 

The tangent of an angle, or arc, is equal to the tangent of 
its supplement. Thus A C, is the tangent of the angle BOA, 
or the arc B A. It is also equal to the tangent of the angle 
BOG, or the arc B E F G, the corresponding supplement of 
the angle BOA, or of the arc B A. 

The Secant of an angle, or arc, is the straight line drawn 
from the centre of the circle through one extremity of the arc 
and limited by the tangent passing through the other ex- 
tremity. Thus O C is the secant of the angle B O A, or of the 
arc B A. 

The secant of an arc is equal to the secant of its supple- 
ment. 

The Co-seeant of an angle, or arc, is equal to the secant of 
its complement. 

Thus E T is the co-secant of the angle BOA, or of the arc 
B A. 

It will be observed that the co-sine, the co-tangent and the 
co-secant are respectively the sine, tangent, and secant of the 
complement of the arc, or in other words, the complement-sine, 
the complement-tangent, and the complement-secant. 

Trolleys. — Rolling contacts that move over the overhead 
lines provided for a line of electric railway cars, and carry off 



WORDS, TERMS AND PHRASES. 611 

the current required to drive the motor car. (See Sled 

Plow.) 

Tubes, Geissler (See Geissler Tubes.) 

Tubes of Force.— (See Force, Tubes of.) 
Tubes of Induction.— See Force, Tubes of.) 

Tubes, Mercury Vacuous glass tubes in 

which a flash of light is produced by the fall of a small quan- 
tity of mercury placed inside it. 

The light is caused by the electricity produced by the friction 
of the mercury in falling against the sides of a spiral glass 
tube placed inside the vacuous tube. 

Tubes, Plucker (See PlilckerTubes.) 

Tubes, Stratification — (See Stratification 

Tubes.) 

Type-Printing Telegraph.— (See Telegraph Print- 
ing.) 

Type writer, Electric A type- writing 

machine in which the keys are intended to make the contacts 
only of the circuits of electro magnets, by the attractions 
of the armatures of which the movements of the type levers 
required for the work of printing are effected. 

Electric typewriters secure a uniformity of impression that 
is impossible to obtain with hand worked machines; they also 
greatly lessen the mechanical labor of writing. — (See Dynamo- 
graph.) 

Ultra Gaseous Matter.— A term sometimes applied to 
radiant matter. — (See Matter, Radiant.) 

Underground Conductors. — Electric conductors 
placed underground by actual burial, or by passing them 
through underground conduits or subways. 

Underground conductors, though less unsightly than the 
ordinary aerial conductors, require to be laid with unusual care 
to render them equally safe, since, when contacts do occur, all 



612 



A DICTIONARY OF ELECTRICAL 



the wires in the same conduit are apt to be simultaneously 
affected, thus spreading- the danger in many different direc- 
tions. They are, however, less liable to danger arising from 
accidental crosses or contacts. 

Undulatory Currents. — (See Currents, Undulatory.) 

filiform Magnetic Field.— A field traversed by the 
same number of lines of magnetic force per unit of area of 
cross section of the field. — (See Fields, Magnetic.) 

Uniform Potential. — A potential that does not vary. 

An electric source is said to generate a uniform potential 
when it maintains a constant difference of potential at the 
terminals. 

Unipolar Induction. — A term sometimes applied to the 
induction that occurs when a conductor is so moved through 
a magnetic field as to continuously cut its lines of force. 

If the conducting wire ABC, Fig. 388, be rotated (in a direc- 
tion towards the ob- 
server) around the 
pole N of a magnet, 
it will continuously 
cut its lines of mag- 
netic force and will 
therefore produce 
continuous cur 
in the direction of 
the arrows. The end 
A is supported in a 
recess in N, while 
the end near C slides 
on a projection on 
the middle of the magnet. Unipolar dynamos operate on the 
continuous cutting of lines of magnetic force. 

Strictly speaking there is no such thing as a unipolar dyn- 
amo, or unipolar induction, since a single magnetic pole can- 




WORDS, TERMS AND PHRASES. 613 

not exist by itself. Continuous cutting- of lines of magnetic 
force, however, can exist and produces, unlike the ordinary 
bi-polar induction, a continuous current. 

Unit Angle. — (See Angular Velocity.) 

Unit, B. A. The British Association unit of resist- 
ance or ohm. — (See Ohm.) 

Unit of Acceleration. — (See Acceleration, Unit of.) 

Unit of Activity. — (See Activity, Unit of.) 

Unit Diflernce of Potential or Electro-Motive 
Force. — Such a difference of potential between two points 
that requires the expenditure of one erg of work to bring* a 
unit of positive electricity from one of these points to the other, 
against the electric force. (See Erg.) 

Unit Jar. — (See Jar, Unit.) 

Unit of Current, Jacobi's A current which 

passed through a voltameter will liberate in one minute a cubic 
centimetre of oxygen and hydrogen at 0° C. and 760 m. m. 
barometric pressure. 

1 

One Jacobi's Unit of Current equals Weber per second. 

(Obsolete.) 10 ' 82 

Unit of Heat, New.— (See Therm.) 
Unit of Hass.— (See Mass, Unit of.) 
Unit of Power.— (See Power, Unit of.) 

Unit of Pressure, New (See Barad.) 

Unit of Resistance, Jacobi's — The electric re- 
sistance of 25 feet of a certain copper wire weighing 345 grains. 
Another unit of electric resistance proposed by Jacobi was 
the resistance of a copper wire one metre in length and one 
millimetre in diameter. 

Unit of Resistance, Matthiessen's The resist- 
ance of one statute mile of pure annealed copper wire \ of 
an inch in diameter at 15.6° C. 



014 A DICTIONARY OF ELECTRICAL 

Unit of Resistance, Varley's —The resistance 

of one statute mile of a special copper wire T X g of an inch in 
diameter. 

Varley's unit was afterwards adjusted by him to equal 25 
Siemens mercury units. 

Unit of Resistance. — Such a resistance that unit dif- 
ference of potential is required to cause a current of unit 
strength to pass. 

Unit Quantity of Electricity.— The quantity of elec- 
tricity conveyed by unit current per second. 

Unit of Supply, Electrical A unit-pro visionally 

adopted in England by the Board of Trade, equal to 1,000 
amperes flowing for one hour under an electro-motive force 
of one volt. 

This would, of course, equal 1,000 watt hours, and would 
be the same as 100 amperes flowing for ten hours under one 
volt. 

One unit of electrical supply is equal to 1.34 actual horse 
power expended for one hour, and will feed 13.4 Swan lamps 
of 21 candle power for one hour. It is equal in illuminating 
power in Swan lamps, to the light produced by 100 cubic feet 
of gas consumed in twenty 14-candle burners in one hour. 

Unit Strength of Current.— Such a strength of current 
that when passed through a circuit one centimetre in length, 
arranged in an arc of one centimetre radius, will exert a 
force of one dyne on a unit magnet pole placed at the 
centre. 

Unit of Velocity, tfew The Kine— (See Kine.) 

Units C. O. S. The centimetre-gramme-second 

units. — (See Units, Fundamental.) 

Units, Derived Various units obtained or derived 

from the fundamental units of Length, L, Mass, M, and Time,T. 
The derived units and their dimensions are as follows : 



Words, terms and phrases. 615 

Area, L 8 . — The Square Centimetre. 

Volume, L 3 . — The Cubic Centimetre. 

Velocity, V. — Unit Distance traversed in Unit Time, or 

L 
V=- • (1) 
T 

Acceleration, A. — The rate of change which will produce a 
change of velocity of one centimetre per second. 

V 
A = — • (2) 

T 

Substituting in equation (2) the value of V in equation (1), 
we have, 

L 

T L 
A = - = - • (3) 



Force, F. — The Dyne, or the force required to act on unit 
mass in order to impart to it unit velocity. 
F = MxA • (4) 
Substituting the value of A derived from equation (2), we 
have, 

V 
F = Mx- • 
T 

Substituting the value of V derived from equation (1), we 
have, 

M L ML 
F=-x-= • (5) 

T T T 2 

Work or Energy, W. — The Erg, or the work done in over- 
coming unit force through unit distance. 

ML ML 2 
W = FxL = xL = • 



616 A DICTIONARY OF ELECTRICAL 

Power, P.— The Unit Rate of Doing Work. 

ML 2 

W T 3 ML 8 

P = - = = • (6) 

T T T s 



Units, Electro-Magnetic A system of units 

derived from the C. G. S. units, employed in electro-magnetic 
measurements. 

Units, Electro-Magnetic, Dimensions of 



f ML 

Current strength = Intensity of Field x Length = 

T 



Quantity = Current x Time = |/M x L . 

Potential. Dif. of Pot. ) Work ^MxL* 

Electro-motive force f Quantity T8 

Electro-motive force L 

Resistance = = — • 

Current T 

Quantity T 2 

Capacity = = — • 

Potential L 

Units, Electrostatic Units based on the force 

exerted between two equal quantities of electricity. 

Two systems of electric units are derived from the C. G. S. 
system, viz., the Electrostatic and the Electromagnetic. These 
units are based respectively on the force exerted between two 
quantities of electricity, and between two magnet poles. 

The electrostatic units embrace the units of Quantity, 
Potential, and Capacity. No particular names have as yet 
been adopted for these units. 

Unit of Quantity. — That quantity of electricity which will 
repel an equal quantity of the same kind of electricity placed 



WORDS, TERMS AND PHRASES. 617 

at a distance of one centimetre from it with the force of one 
dyne. 

Electrostatic potential, or power of doing electrostatic 
work, is measured in units of work, or ergs. 

Unit Difference of Potential. — Such a difference of poten- 
tial between two points as requires the expenditure of one erg 
of work to bring up a unit of positive electricity from one 
point to the other against the electric force. 

Unit of Capacity — Such a capacity of a conductor as re- 
quires a charge of one unit of electricity to raise it to unit 
potential. 

Specific Inductive Capacity. — The ratio between the induc- 
tive capacity of a substance and that of air, measured under 
precisely similar conditions. 

The specific inductive capacity is obtained by comparing the 
capacity of a condenser filled Avith the particular substance, 
and the capacity of the same condenser when filled with air. 
The specific inductive capacity of air is taken as unity. 

Units, Electrostatic, Dimensions of.— 



Quantity : 


= |/ force x 

Quantity 

Time 
Work 


(distance) 2 


, 3 

V 


Y F x L 2 : 




4/MxL 






T 
M^ L 2 




Current = 


MxL 3 
T 2 


Potential = 
Resistance 
Capacity = 


IxL 


Quantity 
Potential 


T 
= L _1 T = 

= L . 


T 
L 


T 


Current 
Quantity 

Potential 





618 A DICTIONARY OF ELECTRICAL 

One Quantity 

Specific Inductive Capacity = = A simple 

Another Quantity 
ratio or number. 

Force , , 

Electro-motive Intensity = — IVP L* T- 1 = 

Quantity 



|/MxL 

T 
The fractional and negative exponents used above are 
merely convenient methods of expressing the contraction of 
roots, and division by the quantity represented by the nega- 
tive exponent. 

Units, Fundamental The units of length, time, 

and mass, to which all other quantities can be referred. 

The unit of length is now generally taken as the Centimetre ; 
the unit of time as the Second ; and the unit of mass as the 
Gramme. These form a system of measurement known as 
the centimetre-gramme-second system, or the C. G. S. system, 
or absolute system. 

The dimensions of the fundamental units, are designated 
thus : 

Length = L. 
Mass = M. 
Time = T. 

Units of Heat. — (See Heat, Units.) 

Units, Magnetic. — Units based on the force exerted be- 
tween two magnet poles. 

Unit Strength of Magnetic Pole. — Such magnetic strength 
of pole that repels another magnetic pole of equal strength 
placed at unit distance with unit force, or one dyne. 

Magnetic Potential. — Power of doing work possessed by a 
magnet pole. 

Magnetic Potential is measured, like electrostatic potential, 
in units of work, or in ergs. 



WORDS, TERMS AND PHRASES. 619 

Magnetic Potential, Unit Difference of. — Such a difference 
of magnetic potential between two points that requires the 
expenditure of one erg of work to bring up a magnetic pole 
of unit strength towards a like pole. 

Unit Intensity of Magnetic Field. — Such an intensity of 
magnetic field as acts on a north-seeking pole of unit strength 
with the force of one dyne. 

Units, Magnetic, Dimensions of 

i/ML 8 

Strength of Pole, or ) = , (Distance) 2 = 

Quantity of Magnetism ) T 

Work |/MxL 
Magnetic Potential = = • 



Intensity of field = 



Strength of pole T 

Force |/~M~ 



Strength of pole L 8 xT 

Units, Practical — Multiples or fractions of the 

absolute or centimetre-gramme-secohd units. 

The practical units have been introduced because the abso- 
lute units are either too small or too large for actual use. 

Electro-motive Force.— The Volt = 100,000,000 C. G. S. or 
absolute units, that is, 10 8 absolute units of resistance. (See 
Volt) 

Resistance. — The Ohm = 1,000,000,000 absolute units of re- 
sistance, or 10 9 absolute units. (See Ohm.) 

Current. — The Ampere = -^ Absolute Unit of Current. 
(See Ampere.) 

Quantity. — The Coulomb = -^ Absolute Unit of Quantity, 
of the electro magnetic system. — (See Coulomb.) 

1 

Capacity. — The Farad = Absolute Unit of Cap- 

1,000,000,000 
acity, or 10 9 units of capacity. (See Farad.) 

Universal Discharger. — (See Discharger, Universal.) 



620 A DICTIONARY OF ELECTRICAL 

Vacuum, Absolute A space from which all 

traces of residual gas have been removed. 

A term sometimes loosely applied to a high vacuum. It is 
doubtful whether an absolute vacuum is attainable by any 
physical means. 

Vacuum, High Such a vacuum that the length 

of the mean free path of the molecules of the residual atmos- 
phere ]s equal to, or exceeds, the dimensions of the containing 
vessel. (See Layer, Crookes'.) 

Vacuum, Low or Partial Such a vacuum 

that the mean free path of the molecules of the residual gas 
is small, as compared with the dimensions of the containing 
vessel. (See Tubes, Geissler.) 

In a high vacuum, groups of molecules can move across the 
containing vessel without meeting other groups of molecules. 
In a low vacuum, such a group of molecules would be broken 
up by collision against other groups before reaching the 
other side of the vessel. 

Vacuum Pumps.— (See Pumps.) 

Vacuum Tubes. — (See Tubes, Vacuum.) 

Valency. — The worth or value of the chemical atoms as 
regards their power of displacing other atoms in chemical 
compounds. (See Atomicity.) 

The worth, or valency, of oxygen is twice as great as that of 
hydrogen, since one atom of oxygen is able to replace two 
hydrogen atoms in chemical combinations. 

Valve-Burner, Electric Argand (See Ar- 

gand Valve-Burner, Electric.) 

Valve, Electric An electrically controlled or 

operated valve. 

In systems of electro-pneumatic signals, gaseous or liquid 
pressure controlled by electrically operated valves, is em- 
ployed to move signals, ring bells, control water and air 
valves, or to perform other similar work. 



WORDS, TERMS AND PHRASES. 



621 



Vapor Globe of Incandescent Lamp.-A glass 
globe surrounding the chamber of an incandescent electric 
lamp, for the purpose of enabling the lamp to be safely used 
in explosive atmospheres, or to 
permit the lamp to be exposed in 
places where water is liable to 
fall on it. 

Such a vapor globe is shown in 
Fig. 389. 

Variable State of Charge 
of Telegraph Line. — (See 
State, Variable.) 

Variation, Annual, Diurn- 
al, Irregular, Secular. 

— (See Declination, Magnetic, Va- 
rieties of.) 

Variation Chart. — (See 
Chart, Variation.) 

Variation Compass.— (See 
Compass, Variation.) 

Variation Needle. — (See 
Needle, Declination.) 

Variations, Magnetic 

— (See Magnetic Variations.) 

Varnish, Electric or 

Insulating Varnish. — A varn- 




Fig. 389. 



ish formed of any good insulating 
material. 

Shellac dissolved in alcohol, applied to a thoroughly dried 
surface and afterwards hardened by baking, forms an excel- 
lent varnish. 



Vegetation, Effects of Electricity on Most 

vegetable fibres contract on the passage of an electric cur- 
rent through them when in the living plant. 



622 A DICTIONARY OF ELECTRICAL 

Velocity, Angular (See Angular Velocity.) 

Velocity of Discharge.— The time required for the pass- 
age of a discharge through a conductor, as compared with its 
length. 

By means of a rapidly revolving mirror Wheatstone meas- 
ured the velocity at which the discharge of aLeyden jar passed 
through half a mile of copper wire as 288,000 miles per second. 

The velocity of discharge through long conductors or cables 
is much lessened by the capacity of the cable and the effects 
of induction, etc. (See Retardation.) 

Velocity Ratio. — A remarkable ratio, in the nature of a 
velocity, that exists between the ratio of the electro-static and 
the electro-magnetic values of the electric units. 

This ratio will be understood from the comparison of the 

following units : 

Mi li T- 1 L 

Quantity = j j — = — = V • 

M* L^ T 

Here the value of the ratio, viz. , the length divided by the 

L 
time, is clearly in the nature of a velocity, for V = — • 

T 
Mi ii T-i T 1 

Potential = — ^ - = — = — • 

M? jj t-2 L V 

L L 2 

Capacity = = — =■ = V* • 

L-i ts t 2 

L _i t T 2 1 

Resistance = = — = — • 

L T- 1 L 2 V 2 
A remarkable similarity exists between the value of the 
velocity expressed in C. G. S. units, and the velocity of light, 
which is of great significance in the electro-magnetic theory 
of light. (See Light, Electro-Magnetic Theory of.) 

The velocity of light is, say, 2.9992 X 10 10 centim. per second. 
The velocity ratio, v, is 2.9800 X 10 10 centimetres per second. 



WORDS, TERMS AND PHRASES. 623 

Ventilation of Armature. — Devices for the free pass- 
age of air or other fluid through the armature of a dynamo- 
electric machine in order to prevent its over-heating. (See 
Dynamo-Electric Machine, Armature, Ventilation of.) 

Vernier. — A device for the approximately accurate 
measurement of smaller differences of length than can be 
readily detected by the eye. 

There are a variety of vernier scales in use. 

Vernier Wire Gauge. (See Wire Gauge, Vernier.) 

Vibration. — A to-and-fro motion of the particles of an 
elastic medium. (See Waves.) 

Vibrations, Sympathetic (See Sympathetic 

Vibrations.) 

Vis-Viva. — The energy stored in a moving body. Hence, 
the measure of the amount of work that must be performed 
in order to bring a moving body to rest. 
M V 

The vis-viva = • 

2 

This term is gradually becoming obsolete. 

Vitreous Electricity. — A term formerly employed to 
indicate positive electricity. 

It was formerly believed that the friction of glass with 
other bodies always produced positive electricity. 

The term is now replaced by positive electricity. (See 
Resinous Electricity.) 

Volcanic Lightning. (See Lightning, Volcanic.) 

Volt. — The practical unit of electro-motive force. 

Such an electro-motive as is induced in a conductor which 
cuts lines of magnetic force at the rate of 100,000,000 per sec. 

Such an electro-motive force as would cause a current of 
one ampere to flow against the resistance of one ohm. 

Such an electro-motive force as would charge a condenser of 
the capacity of one farad with a quantity of electricity equal 
to one coulomb. 



624 A DICTIONARY OF ELECTRICAL 

Volt- Ampere. — The watt or unit of electric power. (See 
Power, Electric.) 

Volt-Meter Oalvanometer.— (See Galvanometer, Volt- 
Meter.) 

Voltaic Alternatives.— (See Alternatives, Voltaic.) 

Voltaic Arc. — (See Arc, Voltaic.) 

Voltaic Battery. — (See Battery, Voltaic.) 

Voltaic Cell. — An electric source consisting of a voltaic 
couple and one or two electrolytes. (See Cell, Voltaic.) 

Voltaic Couple. — Two dissimilar metals, or a metal and 
a metalloid, capable of acting as an electric source, when 
dipped in an electrolyte, or capable of producing a difference 
of electric potential by mere contact. (See Couple, Voltaic.) 

Liquids and gases are capable of acting as voltaic couples. 

Voltaic Element. — One of the two substances that form 
a voltaic couple. (See Couple, Voltaic.) 

Voltaic Electricity.— Electricity produced by the agency 
of a voltaic cell or battery. 

Electricity is the same thing, or phase of energy, by what- 
ever source it is produced. 

Voltaic or Current Induction. — A variety of electro- 
dynamic induction produced by circuits on themselves, or in 
neighboring circuits. (See Induction, Electro-Dynamic.) 

Voltameter. — An electrolytic cell employed for measuring 
the strength of the current passing through it by the amount 
of chemical decomposition effected in a given time. 

Various electrolytes are employed in voltameters, such as 
aqueous solutions of sulphuric acid, copper sulphate, or other 
metallic salts. 

In the water voltameter shown in Fig. 390, the battery 
terminals are connected with platinum electrodes immersed 
in water slightly acidulated with sulphuric acid, and placed 



WORDS, TERMS AND PHRASES. 



635 



inside glass tubes, also filled with acidulated water. On the 
passage of the current, hydrogen appears at the kathode, and 
oxygen at the anode, in nearly the proportion of two volumes 
to one. (See Ozone.) 




Fig. 390. 

In the case of sulphuric acid {hydrogen sulphate) the decom- 
position would appear to be as follows : 

H 2 S0 4 =H 2 + S0 4 . 

The hydrogen appears at the electro negative terminal, or 
kathode. The S0 4 appears at the electro positive terminal or 
anode, but, combines with one molecule of water, thus, 
S0 4 -|- H 2 O = H 2 S0 4 -f- O, gaseous oxygen being given off 
at the anode. 



measurement of electric currents, because a certain electro- 
motive force must be reached before electrolysis is effected. 

The voltameter in reality measures the coulombs, and, 
therefore, is valuable as a current measurer only when the 
current is constant. 

Coulomb-meter would, therefor, be the preferable term. 

Then, again, time is required to produce the results, and 
considerable difficulty is experienced in maintaining the cur- 



626 A DICTIONARY OF ELECTRICAL 

rent strength constant, either on account of variations in the 
electro-motive force of the source, or of variations in the 
resistance of the voltameter. 



Voltameter, Siemens' Differential 



— A form of voltameter employed by Sir Wm. Siemens for de- 
termining the resistance of the platinum spiral m his electric 
pyrometer. (See Pyrometer, Electric.) 

Two separate voltameter tubes provided with platinum 
electrodes and filled with dilute sulphuric acid, are provided 
with carefully graduated tubes to determine the volume of the 
decomposed gases. (See Voltameter.) 

A current from a battery is divided by a suitable commu- 
tator into two circuits connected respectively with the two 
voltameter tubes. In one of these circuits a known resistance 
is placed, in the other the resistance to be measured, i. e., the 
platinum coil used in the electric pyrometer. 

Edison's electric meter consists of a Voltameter. (See Meter, 
Electric.) 

Volt-ammeter. — A variety of galvanometer capable of di- 
rectly measuring both the difference of potential and the am- 
peres. 

Volt-Coulomb. — The unit of electric work. The Joule. 
(See Joule.) 

Voltmeter. — A galvanometer for measuring the electro- 
motive force, or difference of potential, between any two 
points in a circuit. (See Galvanometer.) 

Vulcanized Fibre. — A variety of insulating material 
suitable for purposes not requiring the highest insulation. 

Vulcanized fibre is, however, seriously affected by long ex • 
posure to moisture. 

Vulcanite or Ebonite, — A variety of vulcanized rubber 
extensively used in the construction of electric apparatus. 

Though an excellent insulator, vulcanite will lose its insu- 
lating properties by condensing a film of moisture on its sur- 



WORDS, TERMS AND PHRASES. 627 

face. This can be best removed by the careful application of 
heat. 

The surface is very liable to become covered by a film of 
sulphuric acid due to the gradual oxidation of the sulphur. 
Mere friction will not remove this film, but it may be removed 
by washing with distilled water. A thick coating of varnish 
will obviate this last defect. 

Watchman's Electric Register. — A device for per- 
manently recording the time of a watchman's visit to each 
locality he is required to visit at stated intervals. 

These registers are of a variety of forms. They consist, how- 
ever, in general, of a drum or disc of paper driven by clockwork, 
on which a mark is made by a stylus or pencil, operated by 
the closing of a circuit by a push button pressed or key turned 
by the watchman at each station. 

Water Battery.— (See Battery, Water.) 

Water Dropping Accumulator.— (See Accumulator, 
Water Dropping.) 

Water, Electrolysis of ■ — The decomposition of 

water by the passage through it of an electric current. 

When pure, water does not appear to conduct electricity ; 
it is therefore not quite certain that pure water can be elec- 
trolytically decomposed. The addition of a small quantity of 
sulphuric acid, or of a metallic salt, however, renders its elec- 
trolysis readily accomplished. 

Water-Eevel Alarm. — (See Alarm, Liquid Level.) 

Water Pyrometer.— (See Pyrometer, Water.) 

Watches, Demagnetization of Pro- 

csesses for readily removing magnetism from watches. 

The demagnetization of watches can be readily effected by 
a method proposed by J. J. Wright. The watch is held by 
its chain and slowly lowered to the bottom of a hollow 
conical coil of wire, and then slowly withdrawn from the coil. 



628 



A DICTIONARY OF ELECTRICAL 



The wire is wound on the coil, as shown in Fig. 391, in 
the shape of a cone, viz., with a single turn at the top, and 
gradually increasing in number of turns towards the bottom. 

The conical coil is con- 
nected with a source of 
rapidly alternating cur- 
rents. 

As the watch is low- 
ered in the coil, it be- 
comes gradually mag- 
netized more and more 
powerfully with oppo- 
site polarities, thus com- 
pletely reversing* and 
removing any polarity it 
previously possessed. As 
it is now slowly raised 
from out the hollow cone, 
this magnetization be- 
comes less and less, until, 
Ftg ' 39L if removed from the coni- 

cal coil while high above its apex, all sensible traces of mag- 
netism will have disappeared. 

Watt.— The volt-ampere, or unit of electric work. (See 
Work, Electric, Unit of .) 

Watt-Hour, Watt-Minute, Watt-Second.— Units of 
work. 

Terms employed to indicate the expenditure of an electrical 
power of one watt, for an hour, minute, or second. 

Watt-Meter.— A galvanometer by means of which the 
simultaneous measurement of the difference of potential and 
the current passing is rendered possible. 

The Watt-Meter consists of two coils of insulated wire, one 
coarse and the other fine, placed at right angles to each other 




WORDS, TERMS AND PHRASES. 



629 



as in the ohm-meter, only instead of the currents acting on a 
suspended magnetic needle, they act on each other, as in the 
electro-dynamometer. 

Waves, Amplitude of —(See Amplitude of 

Waves.) 

Waves, Eleetric (See Oscillations, Electric.) 




Fig. 392. 

Waves of Condensation and Rarefaction.— The 

alternate spheres of condensed and rarefied air by means of 
which sound is transmitted. (See Sound Waves.) 

Weber. — A term formerly employed for the unit of elec- 
tric current, and replaced by ampere. (See Ampere.) 



630 A DICTIONARY OF ELECTRICAL 

Weber. — A term proposed by Clausius and Siemens for a 
magnetic pole of unit strength but not adopted. 

This same term was also employed to designate the unit 
strength of current. Now replaced by the term ampere. 

Weight, Atomic (See Atomic Weight.) 

Weight, Breaking of Telegraph Wires.— 

(See Breaking Weight of Telegraph Wires.) 

Welding, Electric Effecting- the welding- union 

of metals by heat of an electric origin. 

In the process of Elihu Thomson, the metals are heated to 
electric incandescence by currents obtained from inverted 
induction coils, and are subsequently pressed or hammered 
together. 

Fig. 392, shows the Thomson apparatus for the Direct System 
of Electric Welding. The dynamo is combined with the weld- 
ing apparatus. The armature contains two separate wind- 
ings ; one of fine wire, in series with the field magnet coils, 
and another of very low resistance, being formed of a 
U-shaped bars of copper. No commutation is used, the alter- 
nating currents being- well adapted for heating* purposes. The 
terminals of these poles are, therefore, directly connected to 
the clamps that hold the bar to the welder. 

Fig. 393, shows the apparatus for the Thomson Indirect 
System of Electric Welding. This system is applicable to 
heavy work, and cases where more than one welding- ma- 
chine is operated by the current from a single dynamo. 

In this case a high tension current is converted into the large 
welding- current employed by means of a suitably proportioned 
transformer. 

The welding process is the same in either system, and con- 
sists essentially in leading the welding current into the pieces 
to be united near their points of junction when brought into 
firm end contact. As the current is lead across the junction 
the temperature rises sufficiently to soften the metal, when 



WORDS, TERMS AND PHRASES. 631 

the pieces are firmly pressed together by the motion, of the 
clamps or holders. 

In the process of Benardos and Olzewski, the heat of the vol- 
taic arc is employed for a somewhat similar process. 
Wheatstone's Balance. — (See Balance, Wheatstone 1 s.) 

Wheel, Barlow'§ or Sturgeon's (See 

Disc, Faraday's.) 




Fig. 393. 

Wheel, Phonic See Phonic Wheel.) 

Wheel, Reaction (See Reaction Wheel.) 

Whirl, Electric A term employed to indicate 

the circular direction of the lines of magnetic force surround- 
ing a conductor conveying an electric current. See Field 
Electro Magnetic,) 



632 



A DICTIONARY OF ELFCTRICAL 



Whistle, Automatic Electric Steam 



steam whistle, employed on foggy days in some systems of rail- 
way signals, when the visual signals can not be seen, in which 
the passage of the steam through the whistle is automatically 
obtained by the closing of an electric contact, or the passage 
of the locomotive over a certain part of the track. 

Wimsliurst Electrical Machine.— A form of convec- 
tion electric machine invented by Wimsliurst. 

Like the Holtz ma- 
chine, the Wimshurst 
machine is a convection 
induction machine. It 
is, however, more effi- 
cient in action, and will 
probably soon super- 
sede the former ma- 
chine. The Wimshurst 
machine consists of two 
shellac-varnished glass 
plates, that are rapidly 
rotated in opposite di- 
rections. Thin metal- 
lic strips are placed on 
the outside of each of 
the plates, in the radial 
positions shown m Fig, 394. These metal strips act both as 
inductors and carriers; the carrier of one plate acting as an 
inductor to the other plate. 

Two curved brass rods, terminating in fine wire brushes 
that touch the plates, are placed as shown, one at the front of 
the plate, and one at the back, at right angles to each other. 
Pairs of conductors, connected together, provided with collect- 
ing points, are placed diametrically opposite each other, as 
shown. Sliding conductors, terminated with metallic balls, 
are provided for discharging the conductors. Leyden jars 




Fig. SOU. 



WORDS, TERMS AND PHRASES. 633 

the inner coatings of which are connected with the two dis- 
charging rods, and the outer coatings together may be em- 
ployed in this as in the Holtz machine. 

The exact action of this machine is not thoroughly under- 
stood. 



Wind, Electric 



The convection stream of air 



particles produced at the extremities of points attached to the 
surface of charged, insulated conductors. (See Convection, 
Electric. Flier, Electric.) 




Fig 305. 

Windage of Dynamo. — A term proposed for the air 
gap between the armature and the pole pieces of a dynamo. 

Winding, Compound (See Compound Wound 

DynaniO-Electric Machine.) 

Winding*. Ampere — (See Turns, Am- 
pere.) 



634 



A DICTIONARY OF ELECTRICAL 



of Coils.— (See Bi-Filar 



for accurately measuring the 



B C 



Hi 



r&\ 



. D 



Windings, Bi-Filar — 

Windings of Coils.) 

Wire Gauge. — A device 
diameter of a wire. 

The round wire gauge, shown in Fig. 395, is very generally 
used for telegraph lines. Notches of varying widths, cut in 
the edges of a circular plate of tempered steel, serve to ap- 
proximately measure the diameter of a wire, the side of the 
wire being passed through the slots. Numbers, indicating the 
different sizes of the wire, are affixed to each of the openings. 

Wire Gauge, Vernier or Micro meter A 

gauge employed for accurately measuring the diameter of 
a wire in thousandths of an inch, based on the principle of 
the vernier or micrometer. See Fig. 396. 

The wire to be measured is 
placed between a fixed support 
B, and the end C, of a long mov- 
able screw, which accurately fits 
a threaded tube a. A thimble D, 
provided with a milled head fits 
over the screw C, and is attached 
to the upper part. The lower civ- 
Fig. 396. cumference of D, is divided into 
a scale of 20 equal parts. The tube a, is graduated into 
divisions equal to the pitch of the screw. Every fifth of these 
divisions is marked as a larger division. 
The principle of the operation of the gauge is as follows : 
Suppose the screw has 50 threads to the inch, the pitch of 
the screw, or the distance between two contiguous threads, 
is, therefore, ■£$, or .02 of an inch. 

One complete turn of the screw will therefore advance the 
sleeve D, over the scale a, the .02 inch. If the screw is only 
moved through one of the 20 parts marked on the end of the 
thimble or sleeve parts, or the ^ of a complete turn, the end 

*"• £', tw or -001 inch. 



w 




words, terms and phrases. 635 

Suppose, now, a wire is placed between B and C, and the 
screw advanced until it fairly fills the space between them, 
and the reading shows two of the larger divisions on the scale 
a, three of the smaller ones, and three on the end of the sleeve 
D. Then 

2 larger divisions of scale a = 0.2 inch 

3 smaller divisions of scale a = .06 

3 divisions on circular scale on D = .006 

Diameter of wire = 0.266 

Serious inconvenience has arisen in practice from the 
numerous arbitrary numbers or sizes of wires employed by 
different manufacturers. These differences are gradually 
leading to the abandonment of arbitrary sizes for wires, and 
employing in place thereof, the diameters directly in inches 
or thousands of an inch. 

Wire, Grounded (See Ground or Earth.) 

Wire, Insulated Wire covered with any insu- 
lating material. 

Cotton and silk are generally employed for insulating pur- 
poses, either alone, or in connection with various gums, resins, 
oi* other materials, which are plastic when heated, but which 
solidify on cooling. India rubber, caoutchouc, and various 
mixtures and compounds are also employed for the same 
purpose. 

For most of the purposes of line wires, high insulating 
powers, combined with a low specific inductive capacity, is 
required in the insulating materials. 

For overhead wires a waterproof covering is necessary. In 
the neighborhood of combustible materials, some fireproof 
covering is desirable. 

Wires, Conduictibility and Sizes of . 

The following tables give the resistance, size, weight per 
foot, etc., of wire according to some of the principal wire 
gauges. 



636 



A DICTIONARY OF ELECTRICAL 



Number, Diameter, Weight, Length, and Resistance of 
Pure Copper Wire. 



AMERICAN GAUGE. 







Weight 




Resistance of Pure Copper 




Diara. 


Sp. Gr. 


-8.889. 


Length. 


at 70° Fahrenheit. 






Grs. per 
Ft. 


Lbs. 




Ohms 


Feet 




No. 


Inches. 


per 1000 


Ft. per 


per 1000 


per 


Ohms per 






feet. 


Lb. 


Ft. 


Ohm. 


Lb. 


0000 


.460 


4475.33 


639.33 


1.56 


.051 


19605.69 


.0000798 


000 


.40964 


3549.07 


507.01 


1.97 


.064 


15547.87 


.000127 


00 


.36480 


2814.62 


402.09 


2.49 


.081 


12330.36 


.000202 





.32495 


2233.28 


319.04 


3.13 


.102 


9783.63 


.000320 


1 


.28930 


1770.13 


252.88 


3.95 


.129 


7754.66 


.00051 


2 


.25763 


140379 


200.54 


4.99 


.163 


6149.78 


.000811 


3 


.22942 


1113.20 


159.03 


6.29 


.205 


4S76.73 


.001289 


4 


.20431 


882.85 


126.12 


7.93 


.259 


3867.62 


.00205 


5 


.18194 


700.10 


100.01 


10.00 


.326 


3067.06 


.00326 


6 


.16202 


555.20 


79.32 


12.61 


.411 


2432.22 


.00518 


7 


.14428 


440.27 


62 90 


15.90 


.519 


1928.75 


.00824 


8 


.12849 


349.18 


49.88 


20.05 


.654 


1529.69 


.01311 


9 


.11443 


276.94 


3956 


25.28 


.824 


1213.22 


.02083 


10 


.10189 


219.57 


31.37 


31.88 


1.040 


961.91 


.03314 


11 


.09074 


174.15 


24.88 


40.20 


1.311 


762.93 


.05269 


12 


.08081 


138.11 


19.73 


50.69 


1.653 


605.03 


.08377 


13 


.07196 


109.52 


15.65 


63.91 


2.084 


479.80 


.13321 


14 


.06408 


86.86 


12.41 


80.5!) 


2.628 


380.51 


.2118 


15 


.05706 


68.88 


9.84 


101.63 


3.314 


301.75 


.3368 


16 


.05082 


54.63 


7.81 


128.14 


4.179 


239.32 


.5355 


17 


.04525 


43.32 


6.19 


161.59 


5.269 


189.78 


.8515 


18 


.04040 


34.35 


4.91 


203.76 


6.645 


150.50 


1.3539 


19 


.03589 


26.49 


3.78 


264.26 


8.617 


116.05 


2.2772 


20 


.03196 


21.61 


3.09 


324.00 


10.566 


94.65 


3.423 


21 


.02840 


17.13 


2.45 


408.56 


13.323 


75.06 


5.443 


22 


.025347 


13.59 


1.94 


515.15 


16.799 


59.53 


8.654 


23 


.022571 


10.77 


1.54 


649.66 


21.185 


47.20 


13.763 


24 


.0201 


8.54 


1.22 


819.21 


26.713 


37.43 


21.885 


25 


.0179 


6.78 


.97 


1032.96 


33.684 


29.69 


34.795 


26 


.01594 


5.37 


.77 


1302.61 


42.477 


23.54 


55.331 


27 


.014195 


4.26 


.61 


1642.55 


53.563 


18.68 


87.979 


28 


.012641 


3.38 


.48 


2071.22 


67.542 


14.81 


139.893 


29 


.011257 


2.68 


.38 


2611.82 


85.170 


11.74 


222.449 


30 


.010025 


2.13 


.30 


3293.97 


107.391 


9.31 


353.742 


31 


.008928 


1.69 


.24 


4152.22 


135.402 


7.39 


562.221 


32 


.00795 


1.34 


.19 


5236.66 


170.765 


5.86 


894.242 


33 


.00708 


1.06 


.15 


6602.71 


215.312 


4.64 


1421.646 


34 


.0063 


.84 


.12 


8328.30 


271.583 


3.68 


2261.82 


35 


.00561 


.67 


.10 


10501.35 


342.413 


2.92 


3596.104 


36 


.005 


.53 


.08 


13238.83 


431.712 


2.32 


5715.36 


37 


.00445 


.42 


.06 


16691.06 


544.287 


1.84 


9084.71 


38 


.003965 


.34 


.05 


20854.65 


686.511 


1.46 


14320.26 


39 


.003531 


.27 


.04 


26302.23 


865 0(6 


1.16 


22752.6 


40 


.003144 


.21 


.03 


33175.94 


109-865 


.92 


36223.58 



WORDS, TERMS AND PHRASES. 



637 



Table Showing the Difference between Wire Gauges. 





London. 


Stubs. Brown & Sharpe's 


, 


.454 


.460 




.425 


.425 


.40964 




.380 


.380 


.36480 




.340 


.340 


.32495 




.300 


.300 


.28930 




.284 


.284 


.25763 




.259 


.259 


.22942 




.238 


.238 


.20431 




.220 


.220 


.18194 




.203 


.203 


.16202 




.180 


.180 


.14428 




.165 


.165 


.12849 




.148 


.148 


.11443 




.134 


.134 


.10189 




.120 


.120 


.09074 




.109 


.109 


.08081 




.095 


.095 


.07196 




.083 


.083 


.06408 




.072 


.072 


.05706 




.065 


.065 


.05082 




.058 


.058 


.04525 




.049 


.049 


.04030 




.040 


.042 


.03589 




.035 


.035 


.03196 




.0315 


.032 


.02846 




.0295 


.028 


.025347 




.027 


.025 


.022571 




.025 


.022 


.0201 




.023 


.020 


.0179 




.0205 


.018 


.01594 




.01875 


.016 


.014195 




.0165 


.014 


.012641 




.0155 


.013 


.011257 




.01375 


.012 


.010025 




.01225 


.010 


.008928 




.01125 


.009 


.00795 




.01025 


.008 


.00708 




.0095 


.007 


.0063 




.009 


.005 


.00561 




.0075 


=004 


.005 




.0065 




.00445 




.00575 




.003965 




.005 




.003531 




.0045 




.003144 



638 



A DICTIONARY OF ELECTRICAL 



New Legal Standard Wire Gauge (English). 

Tables of Sizes, Weights, Lengths and Breaking Strains of 
Iron Wire. 



Size on 


Diameter. 


Section- 
al area 


Weight of 


Length 

of 

Cwt. 


Breaking strains 


Size 
on 


Wire 
Gauge. 


Inch. 


Mi lie- 
metres. 


in sq. 
inches. 


100 
yards 


Mile. 
Lbs. 


Anneal- 
ed. 


Bright. 


Wire 
Gauge 










Lbs. 


Yards. 


Lbs. 


Lbs. 




7/0 


.500 


12.7 


.1963 


193.4 


3404 


58 


10470 


15700 


7/0 


6/0 


.464 


11.8 


.1691 


166.5 


2930 


67 


9017 


13525 


6/0 


5/0 


.432 


11. 


.1466 


144.4 


2541 


78 


7814 


11725 


5/0 


4/0 


.400 


10.2 


.1257 


123.8 


2179 


91 


6702 


10052 


4/0 


3/0 


.372 


9.4 


.1087 


107.1 


1885 


105 


5796 


8694 


3/0 


2/0 


.348 


8.8 


.0951 


93.7 


1649 


120 


5072 


7608 


2/0 


1/0 


.324 


8.2 


.0824 


81.2 


1429 


138 


4397 


6595 


1/0 


1 


.300 


7.6 


.0707 


69.9 


1225 


161 


3770 


5655 


1 


2 


.276 


7. 


.0598 


58.9 


1037 


190 


3190 


4785 


2 


3 


.252 


6.4 


.0499 


49.1 


864 


228 


2660 


3990 


3 


4 


.232 


5.9 


.0423 


41.6 


732 


269 


2254 


3381 


4 


5 


.212 


5.4 


.0353 


34.8 


612 


322 


1883 


2824 


5 


6 


.192 


4.9 


.0290 


28.0 


502 


393 


1544 


2316 


6 


7 


.176 


4.5 


.0243 


24. 


422 


467 


1298 


1946 


7 


8 


.160 


4.1 


.0201 


19.8 


348 


566 


1072 


1608 


8 


9 


.144 


3.7 


.0163 


16. 


282 


700 


869 


1303 


9 


10 


.128 


3.3 


.0129 


12.7 


223 


882 


687 


1030 


10 


11 


.116 


3. 


.0106 


10.4 


183 


1077 


564 


845 


11 


12 


.104 


2.6 


.0085 


8.4 


148 


1333 


454 


680 


12 


13 


.092 


2.3 


.0066 


6.5 


114 


1723 


355 


532 


13 


14 


.080 


2. 


.0050 


5. 


88 


2240 


268 


402 


14 


15 


.072 


1.8 


.0041 


4. 


70 


2800 


218 


326 


15 


16 


.064 


1.6 


.0032 


3.2 


56 


3500 


172 


257 


16 


17 


.056 


1.4 


.0025 


2.4 


42 


4667 


131 


197 


17 


18 


.048 


1.2 


.0018 


1.8 


32 


6222 


97 


145 


18 


19 


.040 


1. 


.0013 


1.2 


21 


9333 


67 


100 


19 


20 


.036 


.9 


.0010 


1. 


18 


11200 


55 


82 


20 



(Issued by the Iron and Steel Wire Mfrs. Association.) 
Wires, Cross (See Cross, Electric.) 



Wires, Crossing. (See Crossing Wires. 



WORDS, TERMS AND PHRASES. 639 

Wood's Button Repeater.— (See Repeater, Tele- 
graphic.) 

Work, Electric.— The Joule. (See Joule.) 

Work, Electric, Unit of The volt-coulomb 

or joule. (See Volt- Coulomb. Joule.) 

Work, Unit of The erg. (See Erg.) 

Yokes of Electro Magnet. — The solid cross pieces of 
iron that join the ends of the field magnet coils of dynamo elec- 
tric machines, or of electro magnets generally. 

Zero Methods.— (See Null Methods.) 

Zero Potential. — The potential that would exist at an 
infinite distance from any electrified body. 

In practice, the potential of the earth is regarded as the zero 
potential. (See Potential, Zero.) 

Zig-zag Lightning. — Forked lightning, (See Lightning, 
Zig-zag.) 

Zinc, Amalgamation of The covering or amal- 
gamation of zinc with a layer of mercury. 

To amalgamate a plate of zinc, its surface is first thoroughly 
cleaned by immersing the plate in dilute sulphuric acid of 
about one part of acid to ten or twelve parts of water, A few 
drops of mercury are then rubbed over its surface, thus coat- 
ing it with a bright metallic film of zinc amalgam. Care must 
be taken not to use too much mercury, since the zinc plate will 
thus be rendered brittle. 

The necessity for amalgamating the zinc arises from the 
loss of energy through local action, on ordinary plates. 

The action of the amalgam appears to be to cover the sur- 
face of the zinc plate with a layer of chemically pure zinc. 
On the polarization of the battery on closing its circuit the zinc 
ends of the zinc-amalgam are turned towards the negative 
plate, thus in effect producing a plate of chemically pure zinc. 



640 A DICTIONARY OF ELECTRICAL, ETC. 

Zincode of Voltaic Cell. — A term formerly employed 
to indicate the zinc terminal or electrode of a voltaic cell. 

The negative electrode or kathode, are preferable terms. 

Zone, Polar A term proposed by De Watteville 

for the zone or region surrounding the therapeutic electrode 
applied to the human body for electric treatment. 

Zone, Peripolar A term proposed by De Watte- 
ville for the zone or region surrounding the polar zone on the 
body of a patient under electro therapeutic treatment. 

Zinc Sender. — A device employed in telegraphic cir- 
cuits, in which, in order to counteract the retardation pro- 
duced by the charge given to the line, a momentary reverse 
current is sent into the line after each signal. 

A zinc sender generally consists of a low resistance Siemens 
relay introduced between the line and the front contact of the 
signaling key. 

THE END. 



APPENDIX 



Balance or Neutral-Wire Ampere Meter.— An 

ampere meter placed in the circuit of the neutral wire, in a 
three-wire system of electric distribution, for the purpose of 
showing tie excess of current passing over one side of the 
system as compared with the other side, when the central 
wire is no longer neutral. 

Balanced metallic Circuit. — A metallic circuit, the 
two sides of which have similar electrical properties. 

Banked Battery.— (See Battery, Banked.) 

Battery, Banked. — A term sometimes applied to a bat- 
tery from which a number of separate circuits are supplied 
with current. 

The term, banked battery, is sometimes applied to a multi- 
ple-arc connected battery. 

Bed* Piece of Dynamo Electric Machine. — The 

frame on which a dynamo is supported. 

The bed-piece is sometimes called the dynamo frame. 

Bell, Night. (See Night Bell) 

Board, Cro§§-Connecting. (See Cross Con- 
necting Board.) 

Box, Cable. (See Cable Box.) 

Box, Junction. (See Junction Box.) 

Branch. — A term applied to any principal distributing 
conductor from which outlets are taken, or taps made. 

Break-Down Switch. — A special switch, employed in 
small three-wire systems, for connecting the positive and nega- 
tive bus-wires in such a manner as to permit the system to 
be supplied with current from the dynamo in use on one side 
of the system only. 



a APPENDIX. 

Bridges. — Heavy copper wires suitably shaped for connect- 
ing the dynamo electric machines in a station to the bus-rods 
or wires. 

Bug'. — A term originally limited to quadruplex telegraphy 
to designate any fault in the operation of the apparatus. 

This term is now employed, to a limited extent, for faults 
in the operation of electric apparatus in general. 

Bug-Trap. — Any device employed to overcome the 
"bug" in quadruplex telegraphy. 

Bu§-Rod§ or Wires. — Heavy copper rods employed in a 
station, to which all the generating dynamos are connected 
and from which the current passes to the different points of 
the distribution system over the feeders. 

Cable Box. — A receptacle provided for holding and secur- 
ing the terminals of a cable, or underground conductor. 

Cable Laid-Up in Layers. — A term applied to a cable, 
all the wires of which are in layers. 

Cable Laid-Up in Reversed Layers.— A term ap- 
plied to a cable in which the conductors, in alternate layers, 
are twisted in opposite directions. 

Cable Laid-Up in Twisted Pairs. — A term applied 
to a cable in which every pair of wires is twisted together. 

Calling-Drop. — An annunciator drop employed to indi- 
cate to the operator in a telegraphic or telephonic system 
that one subscriber wishes to be connected with another. 

Calling- Wire. — A wire employed in a telegraphic or 
telephonic system, by means of which a subscriber communi- 
cates with the central office, or one central office communi- 
cates with another. 

Cam, Listening. (See Listening Cam.) 

Capacity of a Cable.— The electrostatic capacity of 
one conductor of a cable as compared with the capacity of the 
remainder of the conductors grounded. 



APPENDIX. 3 

Centre of Distribution.— In a system of multiple-distri- 
bution, a place where branch cut-outs and switches are placed 
in order to control communication therewith. 

Climbers and Straps.— Devices employed by linemen 
for climbing wooden telegraph poles. 

Colombin. — A name applied to the insulator between the 
parallel carbons of the Jablochkoff candle, consisting of a 
mixture of sulphate of barytes and sulphate of lime. 

Commutating Transformers, Distribution by 

(See System of Electrical Distribution by Commu- 

tating Transformers.) 

Condensers, System of Alternate Current Distri- 
bution by IHeans of (See System of Alternate 

Current Distribution by Means of Condensers.) 

Condensers, System of Continuous Current Dis- 
tribution by Means of (See System of Continu- 
ous Current Distribution by Means of Condensers.) 

Contraplcx Telegraphy.— A name given to a special 
system of duplex telegraphy. 

Cross Arm. — A horizontal beam attached to a pole for the 
support of telegraph, electric light and other electric wires. 

Cross Connecting Board.— In a system of telegraphic 
or telephonic communication, a board to which the line ter- 
minals are run before entering the switchboard, so as to 
readily place any subscriber on any desired section of the 
switchboard, 

Cross Connection, Telephonic A device em- 
ployed in systems of telephonic communication for the pur- 
pose of lessening the bad effects of induction, in which equal 
lengths of adjacent parallel wires are alternately crossed so 
as to alternately occupy the opposite sides of the circuit. 

Cross-Talk.. — In telephony an indistinctness in the speech 
transmitted over any circuit due to this circuit receiving, 



* APPENDIX. 

either by accidental contacts or by induction, the speech 
transmitted over neighboring circuits. 

Curb, Double (See Double Curb.) 

Curb Signaling.— In cable telegraphy a system for avoid- 
ing the effects of retardation by rapidly discharging the cable 
before another electric impulse is sent into it, not by connect- 
ing it to earth, but by reversing the battery and then connect- 
ing to earth before beginning the next signal. 

Curb Signaling, Double Curb In curb signal- 
ing, a method by which the cable, after connection with the 
battery for sending a signal, is subjected to a reverse battery, 
but instead of being put to earth after this connection as in 
single curb signaling, the battery is again reversed and con- 
nected to earth. 

The time during which the cable is connected to the re- 
versed battery before being put to earth, that is, the time 
during which it receives the positive and negative currents 
may be made of any suitable duration. 

Curb Signaling, Single Curb In curb signaling, 

a method by which the cable after connection with the battery 
for sending a signal, is subjected to a reverse battery current 
and then put to earth before again being connected to the 
battery for sending the next signal. 

Cut-out, Duplex (See Duplex Cut-out.) 

Decalescence. — A term proposed by Prof. Elihu Thom- 
son for the absorption of sensible heat which occurs at a cer- 
tain point during the heating of a bar of steel. 

Decalescence will thus be observed to be the reverse of 
recalescence, which is the phenomenon of the emission of 
sensible heat at a certain point during the cooling of a heated 
bar of steel. (See Recalescence.) 

Distribution of Continuous Currents by Means 
of Condensers. — (See System of Continuous Current 
Distribution by Means of Condensers.) 



APPENDIX. 5 

Double Curb. — An instrument invented by Sir William 
Thomson, employed in curb signaling-, by means of which the 
signals are made and the curb, either single or double, in any 
required proportion, is applied automatically. 

Double Curb Signaling. — (See Curb Signaling, 
Double Curb.) 

Double Plug. — A plug so constructed that when in- 
serted in a spring-jack it makes two connections, one at its 
point and one at its shank. (See Spring Jack.) 

Double Trolley System of Electric Railroad*.— 
A system of electric railroad propulsion, in which a double 
trolley is employed to take the the driving current from the 
overhead wires. 

The double trolley system differs from the single trolley 
system in that it employs no earth return. The parallel 
wires also avoid the effects of injurious induction in neighbor- 
ing telegraph or telephone wires. 

Duplex Cut-out. — A cut-out so arranged that when one 
box is fused or melted by an abnormal current, another can 
be immediately substituted for it. 

Electric Thermo Call.— An instrument for sounding 
an alarm when the temperature rises above, or falls below, a 
fixed point. 

In one form of this instrument a needle is moved over a dial 
by a simple thermic device and rings a bell when the tempera- 
ture for which it has been set is attained. The thermo-call 
is applicable to the regulation of the temperature of dwell- 
ings, incubators, hot houses, breweries, drying rooms, etc. 

Feeder. — One of the conducting wires or channels 
through which the current is distributed to the main con- 
ductors. 

Feeder-Switch. — The switch employed for connecting 
or disconnecting each conductor of a feeder from the bus-bars 
in a central station. 



b APPENDIX. 

Feeder-Equalizer,— An adjustable resistance placed 
in the circuit of a feeder for the purpose of regulating the 
difference of potential at the junction box. 

Fire Balls. — A term sometimes applied to globular light- 
ning. (See Lightning, Globular.) 

Force de Cheval.— The French term for horse power. 
The force de cheval is equal to 32,560 foot pounds per minute. 

Frame of Dynamo Electric Machine.— The bed 

piece that supports a dynamo electric machine. 

The frame is sometimes called the dynamo bed piece. 

Graduators. — Devices, generally electro magnets, in- 
serted in a circuit so as to obtain the makes and breaks, 
required in a system of telegraphy, so gradually that they 
fail to influence the diaphragm of a telephone placed in the 
same circuit, and thus to permit a simultaneous telegraphic 
and telephonic transmission over the same wire. 

Ground Detector. — In a system of incandescent lamp 
distribution, a device, placed in the central station, for show- 
ing by the candle power of a lamp, the proximate location 
of a ground on the system. 

Horse Power of Water.— The Indian Government's 
term for horse power developed by falling water. 

The estimate is made by the following simple rule : 15 cubic 
feet of water falling per second through one foot equals 1 
horse power. 

House Main. — A term employed in a system of multiple 
incandescent lamp distribution for the conductor connecting 
the house service conductors with a centre of distribution. 

House-Service Conductor. — A term employed in a 
system of multiple incandescent lamp distribution for that 
portion of the circuit which is included between the service 
cut-out and the centre or centres of distribution, or between 
this cut-out and one or more points on house mains. 



APPENDIX. 7 

Hysteresis. — Molecular friction to magnetic change of 
stress. 

That property of a medium in virtue of which work is done 
in changing the direction or intensity of magnetic force among 
its parts. 

Intercrossing. — In a system of telephonic communica- 
tion, a device for avoiding the disturbing effects of induction 
by alternately crossing equal sections of the line. (See Cross- 
Connections, Telephonic.) 

Joint, Sleeve. (See Sleeve Joint.) 

Junction Box. — A moisture-proof box provided in a 
system of underground conductors to receive the terminals of 
the feeders, and in which connection is made between the 
feeders and the mains from which the current is distributed to 
the individual consumer. 

Kinetic Theory of Matter. — A theory which assumes 
that the molecules of matter are in a constant state of motion 
or vibration towards, or from, one another. 

Applying the kinetic theory of matter to gases, the mole- 
cules of which have great freedom of motion, the mole- 
cules are so far removed from one another as to be but little, 
if any, influenced by their mutual attractions. They are 
therefore assumed to move in straight lines with very great 
velocity until they collide against one another, or against the 
sides of the containing vessel, when they are reflected and 
again run in straight lines in a new path. 

Leg. — In a system of telephonic exchange, a single wire, 
where a ground system is used, or two wires where a metallic 
circuit is employed, for connecting a subscriber with the main 
switchboard, by means of which the subscriber may be legged 
or placed directly in circuit with two or more parties. 

Legging Key-Board. — A key-board employed for the 
purpose of legging an operator into the circuit connecting two 
or more subscribers. 



8 APPENDIX. 

Lines, Overhead. (See Overhead Lines.) 

Listening Cam. — In a telephonic exchange system a 
metallic cam by means of which the operator is placed in cir- 
cuit with a subscriber. 

Main Feeder. — (See Standard or Main Feeder.) 

Main, House (See House Main.) 

Mains, Street (See Street Mains.) 

Matter, Kinetic Theory of (See Kinetic 

Theory of Matter.) 

Motor-Generators. — Dynamo-electric generators in 
which the power required to drive the dynamo is obtained 
from an electric current. 

Motor generators are used in systems of electrical distribu- 
tion for the purpose of changing the potential of the current. 
They consist of dynamos, the armatures of which are furnished 
with two separate windings, of fine and of coarse wire respect- 
ively. One of these, generally the fine wire, receives the 
driving or motor current, usually of high potential, and the 
other, the coarse wire, furnishes the current used, usually of 
low potential. 

Motor-Generators, System of Electric Distribu- 
tion by (See System of Electric Distribution by 

Motor- Generators.) 

Neutral Relay Armature. — A term applied in contra- 
distinction to a polarized relay armature, in which the relay 
armature, consisting of a piece of soft iron wire, closes a local 
circuit whenever its electro-magnet receives an impulse over 
the main line. (See Polarized Armature.) 

Neutral Wire. — The middle wire of a three-wire system 
of electric distribution. 

Night Bell. — In a telephone exchange, a bell switched 
into connection with the shunted circuit of an annunciator 



APPRNDIX. 9 

case, and provided for calling the attention of the night 
operator by its constant ringing to the falling of a drop. 

Outlet. — In a system of incandescent lamp distribution the 
point of attachment for a socket in a fixture. 

Overhead Line. — A term applied to telegraph, tele- 
phone, and electric light or power lines that run overhead, in 
contradistinction to similar lines placed underground. 

Phantom Wires. — A term applied to the additional cir- 
cuits or wires obtained in any single wire or conductor by the 
use of some multiplex telegraphic system. (See Telegraphy, 
Multiplex. Synchronous Multiplex System of Telegraphy.) 

Plionopli'x Telegraphy. — A system of telegraphic 
transmission in which pulsatory currents, superposed on the 
ordinary Morse currents, actuate a modified telephonic re- 
ceiver, and thus permit the simultaneous transmission of 
several separate messages over a single wire without inter- 
ference. 

Platy meter. — An instrument invented by Sir William 
Thomson for comparing the capacities of two condensers. 

Plug's. — Metallic connections in the shape of plugs for 
making or breaking circuits by placing them in, or removing 
them from, metallic sockets connected with the circuits to be 
made or broken. 

Plugging. — Completing a circuit by means of plugs. 

Recalescence. — The property, first pointed out by Bar- 
rett, possessed by steel when cooling after being heated to in- 
candescence, of again becoming incandescent after a certain 
degree of cooling has been effected. 

A steel wire heated at the middle or near one end to a 
bright red, and allowed to cool in a dim light, will be ob- 
served to cool until a low red heat is reached, when it will be 
observed to reheat at some point in the originally heated por- 
tion. This re-heating is manifested by a brighter red spot 



10 APPENDIX. 

which moves along the portion originally heated. This reheat- 
ing is called recalescence, and is due to latent heat (potential 
energy) which, disappearing when the bar was heated, again 
becomes sensible^kinetic energy) on cooling. 

The temperature at which recalescence takes place is 
sensibly the temperature at which heated steel regains its 
magnetizability. 

Relay Armature, Neutral (See Neutral Relay 

Armature.) 

Service Conductor, House (See House 

Service Conductor.) 

Service, Street (See Street Service.) 

Single Curb Signaling.— (See Curb Signaling, Single 
Curb.) 

Sleeve Joint. — A method of joining conducting wires by 
passing them through tubes and then twisting and soldering. 

Stackling a Wire. — Placing an insulator between the 
two ends of a cut wire. 

Standard or Main Feeder. — The main feeder to which 
the standard pressure indicator is connected, and whose pres- 
sure controls the pressure at the ends of all the other feeders. 

The term pressure in the above definition is used in the 
sense of electro-motive force or difference of potential. 

Street Main§. — In a system of incandescent lamp distri- 
bution the conductors through which the current is distri- 
buted from the feeder ends, through cut-outs, to the district to 
be lighted, and from which service wires are taken. 

Street Service. — In a system of incandescent lamp distri- 
bution that portion of the circuit which is included between 
the main and the service cut-out. 

Switch, Break Down —(See Break Down 

Switch.) 



APPENDIX. 11 

System of Alternate Current Distribution by 
Means of Condensers. — A system of alternate current 
distribution in which condensers are employed to transform 
current charges of high potential received from an alternat- 
ing current dynamo, to charges of low potential which are 
fed to the lamps or other electro-receptive devices. 

In the system of McElroy the conversion from high to low 
potential is obtained by making the plates of the condensers 
charged by the dynamo, or primary plates, smaller than the 
secondary plates, the ratio of the area of the primary plates 
to that of the secondary plates being made in accordance with 
the ratio of conversion desired. 

System of Coi tin nous Current Distribution by 
Heans of Condensers. — A system of distribution devised 
by Doubrava in which a continuous current is conducted to 
certain points in the line where a device called a " disjunctor " 
is employed to reverse it periodically and the reversed 
currents so obtained directly used to charge condensers in the 
circuit of which induction coils are placed. 

The condensers are used to feed incandescent lamps or other 
electro-receptive devices. 

System of Electrical Distribution by Commuta- 
ting Transformers. — A system of electrical distribution 
in which motor-generators are used, but neither the armature 
nor the field magnets are revolved, a special commutator 
being employed to change the polarity of the magnetic 
circuits. 

System of Electric Distribution by Motor- 
Generators. — A system of electric distribution in which a 
continuous current of high potential, distributed over a main 
line, is employed at the points where its electric energy is to 
be utilized for driving a motor, which in turn drives a dynamo, 
the current of which is used to energize the electro-receptive 
devices. 



12 APPENDIX. 

In another system of motor-generators the motor and 
dynamo are combined in one machine with a double wound 
armature, the fine wire coils in which receives the high 
potential driving current and the coarse wire coils furnish the 
low potential current used in the distribution circuits. 

System of Simultaneous Telegraphy and Tele- 
phony over a Single Wire.— A system for the simul- 
taneous transmission of telegraphic and telephonic messages 
over a single wire. 

These systems are based, in general, on the fact that a 
gradual make and break in a telephone circuit fails to appreci- 
ably affect a telephone diaphragm. By the use of graduators 
the makes and breaks required for the transmission of the tele- 
graphic dispatch are effected so gradually that they fail to 
appreciably influence the telephone diaphragm and thus per- 
mit simultaneous telegraphic and telephonic transmission over 
a single wire. (See Graduators.) 

Tailings. — False markings received in systems of auto- 
matic telegraphy, due to retardation. 

Telegraphy, Contraplex (See Contraplex 

Telegraphy.) 

Telegraphy, Phonoplex —(See Phonoplex 

Telegraphy.) 

Thermo Call, Electric (See Electric Thermo 

Call.) 

Thermolysis. — A term applied to the chemical decom- 
position of a substance by heat. 

Thermolysis, or dissociation, is an effect produced by the 
action of heat somewhat similiar to the effect of electrolysis, 
or chemical decomposition produced by the passage of an 
electric current. When a chemical substance is heated, the 
vibration of its molecules is attended by an inter-atomic 
vibration of its constituent atoms so that a decomposition 
ensues. If the temperature is not excessive these liberated 



APPENDIX. 13 

atoms recombine with others which they meet, but at higher 
temperatures such recombination is impossible and a perma- 
nent decomposition ensues, called thermolysis or dissociation. 

Torque. — The stress on a shaft due to electro-magnetic 
action, that is, the turning effort exerted by the armature of 
a motor, for instance, under the influence of the current. 

The torque is usually measured in pounds of pull at the end 
of a radius or arm 1 foot in length. 

Transposing. — In a system of telephonic communication 
a device for avoiding the bad effects of induction by alter- 
nately crossing equal consecutive sections of the line. (See 
Cross- Connection, Telephonic.) 

Trolley System, Double for Electric Rail- 
roads. — (See Double Trolley System of Electric Railroads. 

Trunk Lines. — In a system of telephonic communica- 
tion lines connecting distant stations and used by a number 
of subscribers at each end for purposes of intercommunication. 

Triiiiking Switchboard.— A switchboard in which a 
few subscribers only are connected with the operator, thus 
enabling him to obtain any other subscriber by means of 
trunk wires extending to the other sections. 

Units and Terms, Proposed Wew The fol- 
lowing units and terms have recently been proposed by Oliver 
Heaviside, but have not been generally accepted or adopted. 
These definitions are given in Mr. Heaviside's language. 

" Conductance. — Capacity for conducting electricity. 

"Numerically, the ratio, in absolute measure, of the current 
strength to the total electro-motive force in a circuit of uni- 
form flow. A quantity with the nature of a slowness or re- 
ciprocal to a velocity. The practical unit is called the mho." 

"Conductivity. — Conductance per unit volume." 

(i Elastance. — Capacity of a dielectric for opposing electric 
charge or displacement. 



14 APPENDIX. 

"Numerically, the ratio, in absolute measure, of the differ- 
ence of potential in an electrostatic circuit to the total charge 
or displacement therein produced. The reciprocal of per- 
mittance and a quantity of the inverse nature of a length." 

"Elastivity. — Elastance per unit volume of dielectric." 

"Impedance. — Capacity for opposing the variable flow of 
electricity. 

" Numerically, in the absolute measure, the ratio of the total 
electro-motive force to the current strength at any instant in 
a circuit of variable flow. A quantity with the nature of a 
velocity and in any circuit always greater than the resistance." 

"Inductance. — Capacity for magnetic induction. 

" Numerically, in absolute measure, the number of unit lines 
of magnetic force linked with a circuit traversed by the unit 
current strength. Sometimes alluded to as the coefficient of 
self induction. A quantity of the nature of a length." 

"Inductivity. — Specific capacity for magnetic induction. 
" The numerical ratio of the induction in a medium to the 
induction producing it." 

"Permittance. — Electrostatic capacity. Capacity of a dielec- 
tric for assisting charge or displacement. 

"Numerically, the ratio, in absolute measure, of the total 
charge or displacement in an electrostatic circuit, to the dif- 
ference of potential producing it. A quantity with the nature 
of a length." 

"Permittivity. — The numerical ratio of the permittance of 
a dielectric to that of air. 

"Also known as specific inductive capacity." 

"Reluctance. — Capacity for opposing magnetic induction. 

"Numerically, the ratio, in absolute measure, of the magneto- 
motive force in a magnetic circuit to the total induction therein 
produced. A quantity with the nature of the reciprocal of a 
length. Sometimes described as magnetic resistance." 



APPENDIX. 15 

"Reluctancy or Reluctivity. — Reluctance per unit volume. 

"Sometimes described as specific magnetic resistance. A 
numeric, the reciprocal of inductivity." 

"Resistance. — Capacity for opposing the steady flow of 
electricity. 

"Numerically, in absolute measure, the ratio of the total 
electro-motive force to the current strength in a circuit of 
uniform flow. A quantity with the nature of a velocity. The 
practical unit is called the ohm." 

"Resistivity. — Resistance per unit volume ; sometimes 
alluded to as specific resistance." 

Wire, Xe u trsil (See Neutral Wire.) 

Wires, Phantom (See Phantom Wires.) 



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